Explain what is meant by the term " heterogeneous catalysis ".
Give an example and explain how the catalyst works.
In heterogeneous catalysis, the physical state of the catalyst is different from that of the reactants.
Example of heterogeneous catalysis is the reaction between gaseous iodine and hydrogen to form hydrogen iodide catalysed by solid platinum.
Pt(s)
H2(g) + I2(g) ------------> 2HI(g)
Solid platinum provides a suitable surface for the adsorption of the hydrogen and iodine molecules. This is possible because platinum has many empty or half-filled d-orbitals that can be used to form temporary bonds with the reacting molecules.
The adsorption process not only increases the concentration of the reactants on the platinum surface, it also weakens the covalent bonds in the molecules which leads to a decrease in the activation energy. Furthermore, the reacting molecules are now in the correct orientation for new bonds to be formed.
----H----H----I----I----H----H----I----I----H----H----
temporary bonds
____________________________________________
Platinum surface
* the bonds between H-H and I-I are being broken.
* the bonds between H-I are being formed
After that, the HI molecules are released from platinum surface so that other reactant molecules can be adsorbed.
Monday 9 November 2009
HOMOGENEOUS CATALYSIS
Explain what is meant by the term "homogeneous catalysis".
Give an example and explain how the catalyst works.
Homogeneous catalysis is a reaction where the physical states of the catalyst is the same as that of the reactants.
Example of homogeneous catalysis is the reaction between aqueous iodide ion and aqueous peroxodisulphate ion catalysed by aqueous iron(III) ion.
Fe3+
S2O82-(aq) + 2I-(aq) ------------> I2(aq) + 2SO42-(aq)
In the presence of aqueous iron(III) ion, the reaction occurs in two steps.
Step 1 : 2Fe3+(aq) + 2I-(aq) ----------> 2Fe2+(aq) + I2(aq)
Step 2 : 2Fe2+(aq) + S2O82-(aq) ----------> 2Fe3+(aq) + 2SO42-(aq)
The catalysed reaction has lower activation energy because it involves the collision of oppositely charged particles while the uncatalysed reaction involves the collision of like charged particles.
Homogeneous catalyst works by forming an intermediate (Fe2+) and then being regenerated in the following step. Fe3+ ion manages to do so because it can vary its oxidation states between +3 and +2. By doing so, it helps to transfer the electron from I- to S2O82-.
Give an example and explain how the catalyst works.
Homogeneous catalysis is a reaction where the physical states of the catalyst is the same as that of the reactants.
Example of homogeneous catalysis is the reaction between aqueous iodide ion and aqueous peroxodisulphate ion catalysed by aqueous iron(III) ion.
Fe3+
S2O82-(aq) + 2I-(aq) ------------> I2(aq) + 2SO42-(aq)
In the presence of aqueous iron(III) ion, the reaction occurs in two steps.
Step 1 : 2Fe3+(aq) + 2I-(aq) ----------> 2Fe2+(aq) + I2(aq)
Step 2 : 2Fe2+(aq) + S2O82-(aq) ----------> 2Fe3+(aq) + 2SO42-(aq)
The catalysed reaction has lower activation energy because it involves the collision of oppositely charged particles while the uncatalysed reaction involves the collision of like charged particles.
Homogeneous catalyst works by forming an intermediate (Fe2+) and then being regenerated in the following step. Fe3+ ion manages to do so because it can vary its oxidation states between +3 and +2. By doing so, it helps to transfer the electron from I- to S2O82-.
Saturday 7 November 2009
SHAPE OF MOLECULES
For these compounds - H2S, CIF3, XeF4
a) predict the shape of the molecular orbitals around the central atom
b) explore the shape of the actual molecule and give the change in the angle size and the reason
for it
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
S(6e) ; 2H(2e) ; Total = 8 electrons = 4 electron pairs
The basic shape is tetrahedral.
But there are 2 bond pairs and 2 lone pairs
So, it is V-shaped with bond angle around 104.5 degree
( the strength of electron pairs repulsion decreases from lone pair-lone pair > lone pair-bond pair > bond pair-bond pair )
Cl(7e) ; 3F(3e) ; Total = 10 electrons = 5 electron pairs
The basic shape is trigonal bipyramidal
But there are 2 lone pairs and 3 bond pairs.
The 2 lone pairs are situated on the trigonal plane because they are 120 degree apart.
So, it is T-shaped.
Xe(8e) ; 4F(4e) ; Total = 12 electrons = 6 electron pairs
The basic shape is octahedral.
But there are 2 lone pairs and 4 bond pairs.
The 2 lone pairs are opposite to each other.
So, its shape is square planar.
a) predict the shape of the molecular orbitals around the central atom
b) explore the shape of the actual molecule and give the change in the angle size and the reason
for it
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
S(6e) ; 2H(2e) ; Total = 8 electrons = 4 electron pairs
The basic shape is tetrahedral.
But there are 2 bond pairs and 2 lone pairs
So, it is V-shaped with bond angle around 104.5 degree
( the strength of electron pairs repulsion decreases from lone pair-lone pair > lone pair-bond pair > bond pair-bond pair )
Cl(7e) ; 3F(3e) ; Total = 10 electrons = 5 electron pairs
The basic shape is trigonal bipyramidal
But there are 2 lone pairs and 3 bond pairs.
The 2 lone pairs are situated on the trigonal plane because they are 120 degree apart.
So, it is T-shaped.
Xe(8e) ; 4F(4e) ; Total = 12 electrons = 6 electron pairs
The basic shape is octahedral.
But there are 2 lone pairs and 4 bond pairs.
The 2 lone pairs are opposite to each other.
So, its shape is square planar.
POLAR MOLECULE
Why is CBr2Cl2 considered to be polar?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
In order for a molecule to be polar, it must have polar bond and the molecule must be asymmetrical (not symmetry).
CBr2Cl2 is tetrahedral in shape. It has polar bonds in C-Br and C-Cl. Its shape is not symmetrical. Hence, it is a polar molecule.
Although its shape looks symmetrical, in fact it is not in 3D. The dipole moments of the two C-Br bonds cannot cancel out each other. The same is true of the two C-Cl bonds.
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
In order for a molecule to be polar, it must have polar bond and the molecule must be asymmetrical (not symmetry).
CBr2Cl2 is tetrahedral in shape. It has polar bonds in C-Br and C-Cl. Its shape is not symmetrical. Hence, it is a polar molecule.
Although its shape looks symmetrical, in fact it is not in 3D. The dipole moments of the two C-Br bonds cannot cancel out each other. The same is true of the two C-Cl bonds.
Tuesday 3 November 2009
RATE CONSTANT
Resolved Question
Chemistry - rate of constant (k) problem?
For a reaction aA → products, the initial concentration of A, [A]0 = 6.6 M, and the first half-life is 17 s and the second half-life is 34 s.
What is the numerical value of the rate constant k?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
You will notice that the second half life is two times the duration of the first half life. This is the characteristic of second order reaction.
The second order equation is 1/[A] = kt + 1/[A]o
At first half life t', [A] = [A]o/2
substitute into the equation
2/[A]o = kt' + 1/[A]o
kt' = 1/[A]o
k (17) = 1/6.6
k = 8.91 x 10^-3
Chemistry - rate of constant (k) problem?
For a reaction aA → products, the initial concentration of A, [A]0 = 6.6 M, and the first half-life is 17 s and the second half-life is 34 s.
What is the numerical value of the rate constant k?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
You will notice that the second half life is two times the duration of the first half life. This is the characteristic of second order reaction.
The second order equation is 1/[A] = kt + 1/[A]o
At first half life t', [A] = [A]o/2
substitute into the equation
2/[A]o = kt' + 1/[A]o
kt' = 1/[A]o
k (17) = 1/6.6
k = 8.91 x 10^-3
CONDUCTIVITY IN METAL AND ELECTROLYTE
Resolved Question
Why is it that the conductivity of metals decrease with increase in temperature while that of electrolytes 'increase' with increase in temperature?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
In metal, electron is responsible as the charge carrier. A systematic flow of electrons in one direction will cause the metal to conduct electricity efficiently. An increase in temperature will cause the electrons to get excited and this causes them to move in a not so orderly manner. Hence, they become less efficient as the charge carrier and conductivity decreases.
In electrolyte, it is the ions (both positive and negative) that is responsible as the charge carrier. An increase in temperature will increase the energy of the ions and they will move faster. Hence its efficiency as charge carrier increases and this will cause the conductivity to increase.
Asker's Comment:
thankyou. dats exactly wat i needed to know
Why is it that the conductivity of metals decrease with increase in temperature while that of electrolytes 'increase' with increase in temperature?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
In metal, electron is responsible as the charge carrier. A systematic flow of electrons in one direction will cause the metal to conduct electricity efficiently. An increase in temperature will cause the electrons to get excited and this causes them to move in a not so orderly manner. Hence, they become less efficient as the charge carrier and conductivity decreases.
In electrolyte, it is the ions (both positive and negative) that is responsible as the charge carrier. An increase in temperature will increase the energy of the ions and they will move faster. Hence its efficiency as charge carrier increases and this will cause the conductivity to increase.
Asker's Comment:
thankyou. dats exactly wat i needed to know
EQUILIBRIUM
Resolved Question
Equilibrium Question
CaCO3, CaO and CO2 are at equilibrium. The Following actions are taken:
1. More CO2(g) is added to the system
2. More CaCO3(s) is added to the system
3. Decreased the Volume of the system,
4. Increased the temperature of the system
One or more of there actions lead to a change in CO2(g) concentration after equilibrium is re-established.
Which statements are responsible?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
CaCO3(s) <=========> CaO(s) + CO2(g)
You should use the Le Chatelier's Principle to predict the outcome.
It states that when a system in equilibrium is disturbed, the system will shift its equilibrium position in the direction so as to partially couteract the changes made until a new equilibrium is reestablished.
1. when more CO2 is added, the equilibrium position will shift to the left
2. when more CaCO3(s) is added, it will not change the equilibrium position. The equilibrium
position does not depend on the amount of solid reactants or solid products as long as there is
some solid left in the system.
3. decrease the volume will cause the pressure to increase. Increase in pressure will cause the
equilibrium position to shift to the left as there is less number of moles of gas on the left hand
side of the equation (zero as oppose to one one the right hand side)
4. increase the temperature willl cause the equilibrium position to shift to the right because the
forward reaction is endothermic.So, the answer is 1, 3 and 4
Equilibrium Question
CaCO3, CaO and CO2 are at equilibrium. The Following actions are taken:
1. More CO2(g) is added to the system
2. More CaCO3(s) is added to the system
3. Decreased the Volume of the system,
4. Increased the temperature of the system
One or more of there actions lead to a change in CO2(g) concentration after equilibrium is re-established.
Which statements are responsible?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
CaCO3(s) <=========> CaO(s) + CO2(g)
You should use the Le Chatelier's Principle to predict the outcome.
It states that when a system in equilibrium is disturbed, the system will shift its equilibrium position in the direction so as to partially couteract the changes made until a new equilibrium is reestablished.
1. when more CO2 is added, the equilibrium position will shift to the left
2. when more CaCO3(s) is added, it will not change the equilibrium position. The equilibrium
position does not depend on the amount of solid reactants or solid products as long as there is
some solid left in the system.
3. decrease the volume will cause the pressure to increase. Increase in pressure will cause the
equilibrium position to shift to the left as there is less number of moles of gas on the left hand
side of the equation (zero as oppose to one one the right hand side)
4. increase the temperature willl cause the equilibrium position to shift to the right because the
forward reaction is endothermic.So, the answer is 1, 3 and 4
CATHODIC PROTECTION
Resolved Question
Based of the standard reduction potentials provided below, which of the following metals could provide cathodic protection to keep iron metal from corroding?
(Select all that apply.)
Half-Reaction E° (V)
Ag+(aq) + e‾ → Ag(s) +0.80
Co2+(aq) + 2 e‾ → Co(s) -0.28
Cr3+(aq) + 3 e‾ → Cr(s) -0.74
Cu2+(aq) + 2 e‾ → Cu(s) +0.15
Fe2+(aq) + 2 e‾ → Fe(s) -0.44
Ni2+(aq) + 2 e‾ → Ni(s) -0.25
Mg2+(aq) + 2 e‾ → Mg(s) -2.37
Zn2+(aq) + 2 e‾ → Zn(s) -0.76
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
For cathodic protection of iron from corroding, all you need is to find a metal which is more electropositive than iron. So, you have to choose the metals that have the standard reduction potentials which are more negative than that of iron.
Since E(Fe2+/Fe) = - 0.44 v, Cr(-0.74), Mg(-2.37) and Zn(-0.76) can be used.
Of course, Mg is the best and most efficient as it has the most negative SRP (most electropositive)
Asker's Comment:
Thank you
Based of the standard reduction potentials provided below, which of the following metals could provide cathodic protection to keep iron metal from corroding?
(Select all that apply.)
Half-Reaction E° (V)
Ag+(aq) + e‾ → Ag(s) +0.80
Co2+(aq) + 2 e‾ → Co(s) -0.28
Cr3+(aq) + 3 e‾ → Cr(s) -0.74
Cu2+(aq) + 2 e‾ → Cu(s) +0.15
Fe2+(aq) + 2 e‾ → Fe(s) -0.44
Ni2+(aq) + 2 e‾ → Ni(s) -0.25
Mg2+(aq) + 2 e‾ → Mg(s) -2.37
Zn2+(aq) + 2 e‾ → Zn(s) -0.76
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
For cathodic protection of iron from corroding, all you need is to find a metal which is more electropositive than iron. So, you have to choose the metals that have the standard reduction potentials which are more negative than that of iron.
Since E(Fe2+/Fe) = - 0.44 v, Cr(-0.74), Mg(-2.37) and Zn(-0.76) can be used.
Of course, Mg is the best and most efficient as it has the most negative SRP (most electropositive)
Asker's Comment:
Thank you
ANODISATION
What is the chemical process taking place in sulphuric acid anodizing?
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
Anodising is a process to form a uniform layer of aluminium oxide on aluminium. This is done by the electrolysis process using aluminium as the anode, platinum or other inert substance as cathode and sulphuric acid as the electrolyte.
At the cathode, hydrogen gas is produced. 2H+ + 2e ----> H2
At the anode, oxygen gas is produced. 4OH- ---> 2H2O + O2 + 4e
The oxygen gas produced at the anode (aluminium) will react with Al to form aluminium oxide.
1 week ago
100% 1 Vote
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Voters
Anodising is a process to form a uniform layer of aluminium oxide on aluminium. This is done by the electrolysis process using aluminium as the anode, platinum or other inert substance as cathode and sulphuric acid as the electrolyte.
At the cathode, hydrogen gas is produced. 2H+ + 2e ----> H2
At the anode, oxygen gas is produced. 4OH- ---> 2H2O + O2 + 4e
The oxygen gas produced at the anode (aluminium) will react with Al to form aluminium oxide.
1 week ago
100% 1 Vote
Sunday 27 September 2009
Vapor Pressure of a Solution of a Non-Volatile Solute
Vapor Pressure of a Solution of a Non-Volatile Solute.?
A solution is made by dissolving 32.5g of urea (H2NCONH2, a non-volatile non-electrolyte) in 284g of water.
Calculate the vapour pressure of this solution at 50°C. (note the vapour pressure of pure water at 50°C is 92.5 torr.)
Chemistry
Best Answer - Chosen by Asker
Number of moles of urea = 32.5 / 60 = 0.542 mol
Number of moles of water = 284/18 = 15.778 mol
Mole fraction of water = 15.778 / ( 15.778 + 0.542) = 0.967
Using Raoult's Law,
Vapour pressure = 0.967 x 92.5 = 89.45 torr.
A solution is made by dissolving 32.5g of urea (H2NCONH2, a non-volatile non-electrolyte) in 284g of water.
Calculate the vapour pressure of this solution at 50°C. (note the vapour pressure of pure water at 50°C is 92.5 torr.)
Chemistry
Best Answer - Chosen by Asker
Number of moles of urea = 32.5 / 60 = 0.542 mol
Number of moles of water = 284/18 = 15.778 mol
Mole fraction of water = 15.778 / ( 15.778 + 0.542) = 0.967
Using Raoult's Law,
Vapour pressure = 0.967 x 92.5 = 89.45 torr.
Thursday 24 September 2009
Electrophilic Substitution
Resolved Question
Electrophilic substitution?
Which of the following are all meta directing and activating substituents in aromatic electrophilic substitution reactions?
a. methoxy group, chloride group, nitro group
b. none known
c. bromide group, methyl group, phenyl group
d. aldehyde group, nitro group, carboxylic acid group, ketone group
e. hydroxyl group, amino group, phenyl group
by joeyeehu...
d.
Activating substituents means it activates the substitution reaction. It makes the reaction to proceed faster. A substituent that is an electron donating group will activate the benzene ring.
It increases the electron charge density of the benzene ring and it becomes more susceptible for the attack of an electrophile.
Electrophilic substitution?
Which of the following are all meta directing and activating substituents in aromatic electrophilic substitution reactions?
a. methoxy group, chloride group, nitro group
b. none known
c. bromide group, methyl group, phenyl group
d. aldehyde group, nitro group, carboxylic acid group, ketone group
e. hydroxyl group, amino group, phenyl group
by joeyeehu...
d.
Activating substituents means it activates the substitution reaction. It makes the reaction to proceed faster. A substituent that is an electron donating group will activate the benzene ring.
It increases the electron charge density of the benzene ring and it becomes more susceptible for the attack of an electrophile.
Wednesday 16 September 2009
Solvent Extraction
Resolved Question
1. what are the advantages or disadvantage of using ether as an extraction solvent?
2. in extracting an organic compound from an aquous solution, what practical advantage ensues
if the organic solvent used is more dense than water?
3. why must the stopper be removed from a separatory funnel before the liquid can be
withdrawn from it?
by joeyeehu...
Best Answer - Chosen by Voters
Advantages:
1. it is a great solvent. It can dissolve most of the organic compounds.
2. it has low boiling point. It can be distilled over easily
3. it is chemically inert.
Disadvantage:
1. highly flammable
2. toxic
Q2: It will form two separate distinct layers. So it can be separated easily.
Q3: The stopper must be removed so that the air pressure will help push the liquid out of the
funnel. If not, the flow of liquid is obstructed.
1. what are the advantages or disadvantage of using ether as an extraction solvent?
2. in extracting an organic compound from an aquous solution, what practical advantage ensues
if the organic solvent used is more dense than water?
3. why must the stopper be removed from a separatory funnel before the liquid can be
withdrawn from it?
by joeyeehu...
Best Answer - Chosen by Voters
Advantages:
1. it is a great solvent. It can dissolve most of the organic compounds.
2. it has low boiling point. It can be distilled over easily
3. it is chemically inert.
Disadvantage:
1. highly flammable
2. toxic
Q2: It will form two separate distinct layers. So it can be separated easily.
Q3: The stopper must be removed so that the air pressure will help push the liquid out of the
funnel. If not, the flow of liquid is obstructed.
Polar Molecule
Resolved Question
Which of the following molecules may be polar: S03, XeF4, S F4 1 day ago
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
First, calculate the number of electrons around the central atom. You can use the Group number in the Periodic Table to help you.
Next, determine the number of electron pair around the central atom and state the geometrical arrangement of electron pairs.
2 pairs - linear
3 pairs - trigonal planar
4 pairs - tetrahedral
5 pairs - trigonal bipyramidal
6 pairs - octahedral
Determine the number of bond pairs and lone pairs.
Determine the shape of the molecule.
1) SO3
S--> 6
O---> 3(2) = 6
total 12 electrons = 6 electron pairs
sulphur forms three double bonds with three oxygen.
The shape is trigonal planar. (non polar)
2) XeF4
Xe - 8e
4F - 4e
Total = 12 e = 6 pairs
Basic electron pair arrangement is octahedral
4 bond pair and 2 lone pair
The shape is square planar (non polar)
3) SF4
S = 6e
F = 4e
Total =10e = 5 electron pairs
Basic electron pair arrangement = trigonal bipyramidal
4 bond pair and 1 lone pair
The shape is irregular or see-saw shaped (polar)
Which of the following molecules may be polar: S03, XeF4, S F4 1 day ago
by joeyeehu...
Contributing In:
Chemistry
Best Answer - Chosen by Asker
First, calculate the number of electrons around the central atom. You can use the Group number in the Periodic Table to help you.
Next, determine the number of electron pair around the central atom and state the geometrical arrangement of electron pairs.
2 pairs - linear
3 pairs - trigonal planar
4 pairs - tetrahedral
5 pairs - trigonal bipyramidal
6 pairs - octahedral
Determine the number of bond pairs and lone pairs.
Determine the shape of the molecule.
1) SO3
S--> 6
O---> 3(2) = 6
total 12 electrons = 6 electron pairs
sulphur forms three double bonds with three oxygen.
The shape is trigonal planar. (non polar)
2) XeF4
Xe - 8e
4F - 4e
Total = 12 e = 6 pairs
Basic electron pair arrangement is octahedral
4 bond pair and 2 lone pair
The shape is square planar (non polar)
3) SF4
S = 6e
F = 4e
Total =10e = 5 electron pairs
Basic electron pair arrangement = trigonal bipyramidal
4 bond pair and 1 lone pair
The shape is irregular or see-saw shaped (polar)
Standard Reduction Potential
Resolved Question
Standard reduction potential for Pt2+/Pt?
An electrochemical cell of notation Pt/Pt2+ Ni2+/Ni has Eo = -1.45 V.
If we know that the standard reduction potential of Ni2+/Ni is Eo = -0.25 V,
what is the standard reduction potential for Pt2+/Pt?
Chemistry
Best Answer - Chosen by Asker
From the cell diagram given,
E(Pt2+/Pt) = aode (oxidation) and
E(Ni2+/Ni) = cathode (reduction)
Eo cell = E (reduction) - E ( oxidation)
.......... = E (Ni2+/Ni) - E (Pt2+/Pt)
-1.45 = -0.25 - E(Pt2+/Pt)E(Pt2+/Pt)
= 1.45 - 0.25
= 1.20 V
Asker's Comment:
Thank you
Standard reduction potential for Pt2+/Pt?
An electrochemical cell of notation Pt/Pt2+ Ni2+/Ni has Eo = -1.45 V.
If we know that the standard reduction potential of Ni2+/Ni is Eo = -0.25 V,
what is the standard reduction potential for Pt2+/Pt?
Chemistry
Best Answer - Chosen by Asker
From the cell diagram given,
E(Pt2+/Pt) = aode (oxidation) and
E(Ni2+/Ni) = cathode (reduction)
Eo cell = E (reduction) - E ( oxidation)
.......... = E (Ni2+/Ni) - E (Pt2+/Pt)
-1.45 = -0.25 - E(Pt2+/Pt)E(Pt2+/Pt)
= 1.45 - 0.25
= 1.20 V
Asker's Comment:
Thank you
Friday 11 September 2009
Hybridised Orbital
Resolved Question
Which of the following compounds contain an sp2 hybridised carbon atom?
a) n-butane
b) propanal
c) propanol
d) 2,3-dimethylheptane
by joeyeehu...
Chemistry
In sp2 hybridised carbon atom, it must be bonded to 3 groups or atoms. Normally, the carbon atom must form a double bond in order to be bonded to three groups/atoms instead of four.
Only propanal contains an sp2 hybridesed orbitals.
In CH3CH2CHO, the first carbon is sp3 hybridesed ( it is bonded to four groups/atoms, ie, three hydrogen and CH2CHO).
The second carbon is also sp3 hybridised. ( one CH3, two H and one CHO)The third carbon is sp2.( one CH3CH2, one H and one O)
This rule only applies to carbon atom.
Which of the following compounds contain an sp2 hybridised carbon atom?
a) n-butane
b) propanal
c) propanol
d) 2,3-dimethylheptane
by joeyeehu...
Chemistry
In sp2 hybridised carbon atom, it must be bonded to 3 groups or atoms. Normally, the carbon atom must form a double bond in order to be bonded to three groups/atoms instead of four.
Only propanal contains an sp2 hybridesed orbitals.
In CH3CH2CHO, the first carbon is sp3 hybridesed ( it is bonded to four groups/atoms, ie, three hydrogen and CH2CHO).
The second carbon is also sp3 hybridised. ( one CH3, two H and one CHO)The third carbon is sp2.( one CH3CH2, one H and one O)
This rule only applies to carbon atom.
Friday 4 September 2009
Strongest acid ?
Resolved Question
Acids... which is stronger?
Which one of the following is the strongest acid?
(a) ICH2CO2H
(b) BrCH2CO2H
(c) ClCH2CO2H
(d) FCH2CO2H
(e) ICH2CH2CO2H
by joeyeehu...
Chemistry
The answer is (d).
A strong acid is the one that can donate a proton(H+) easily.The presence of halogen will increase the ability of the acid to donate proton. This is so because halogen being more electronegative will attract the electrons toward itself. This will reduce the electron charge density of the OH bond (COOH). It weakens the OH bond and hence it becomes easier for the H+ to be donated.
Since F is the most electronegative among the halogen, it has the strongest effect ( negative inductive effect ). It weakens the OH bond the most and it will cause the molecule to donate H+ readily.
Acids... which is stronger?
Which one of the following is the strongest acid?
(a) ICH2CO2H
(b) BrCH2CO2H
(c) ClCH2CO2H
(d) FCH2CO2H
(e) ICH2CH2CO2H
by joeyeehu...
Chemistry
The answer is (d).
A strong acid is the one that can donate a proton(H+) easily.The presence of halogen will increase the ability of the acid to donate proton. This is so because halogen being more electronegative will attract the electrons toward itself. This will reduce the electron charge density of the OH bond (COOH). It weakens the OH bond and hence it becomes easier for the H+ to be donated.
Since F is the most electronegative among the halogen, it has the strongest effect ( negative inductive effect ). It weakens the OH bond the most and it will cause the molecule to donate H+ readily.
Monday 31 August 2009
Conductivity of Giant Molecule
Resolved Question
Why giant ionic substance conduct electricity and why giant substances (except graphite) do not?
by joeyeehu...
Chemistry
Best Answer - Chosen by Voters
Giant ionic substance can conduct electricity only in aqueous state or in molten state. In solid state, it cannot conduct electricity because the ions are not mobile.
Giant metallic substance can conduct electricity either in solid or in molten states. This is so because it has delocalised electrons that can act as charge carrier.
Giant covalent compounds cannot conduct electricity neither in solid nor molten states.
Although graphite is a covalently bonded, it has one delocalised electron per carbon atom.
( sp2 hybridised orbitals). Hence it can conduct electricity.
Why giant ionic substance conduct electricity and why giant substances (except graphite) do not?
by joeyeehu...
Chemistry
Best Answer - Chosen by Voters
Giant ionic substance can conduct electricity only in aqueous state or in molten state. In solid state, it cannot conduct electricity because the ions are not mobile.
Giant metallic substance can conduct electricity either in solid or in molten states. This is so because it has delocalised electrons that can act as charge carrier.
Giant covalent compounds cannot conduct electricity neither in solid nor molten states.
Although graphite is a covalently bonded, it has one delocalised electron per carbon atom.
( sp2 hybridised orbitals). Hence it can conduct electricity.
CaF2 - Acidic or Basic
Resolved Question
Is CaF2 (calcium fluoride) acidic or basic? Is Ca(OH)2 a strong or weak base?
So I learned to look at where each ion came from.
Ex: NaCl is a neutral salt because NaOH is a strong base and HCl is a strong acid.
If you have NaF, this is slightly basic since NaOH is a strong base and F comes
from HF which is a weak acid...
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by joeyeehu...
Chemistry
Best Answer - Chosen by Voters
You are right. CaF2 is slightly basic.The reason is HF is a weak acid ( but it is very corrosive).When dissolved in water, the F- ion formed will undergoes hydrolysis reaction with water molecules forming HF and OH-. Thats why, it is basic.
F- + H2O ---------------> HF + OH-
Ca(OH)2 is a strong base.
Is CaF2 (calcium fluoride) acidic or basic? Is Ca(OH)2 a strong or weak base?
So I learned to look at where each ion came from.
Ex: NaCl is a neutral salt because NaOH is a strong base and HCl is a strong acid.
If you have NaF, this is slightly basic since NaOH is a strong base and F comes
from HF which is a weak acid...
Report Abuse
by joeyeehu...
Chemistry
Best Answer - Chosen by Voters
You are right. CaF2 is slightly basic.The reason is HF is a weak acid ( but it is very corrosive).When dissolved in water, the F- ion formed will undergoes hydrolysis reaction with water molecules forming HF and OH-. Thats why, it is basic.
F- + H2O ---------------> HF + OH-
Ca(OH)2 is a strong base.
Thursday 27 August 2009
Bond length
Open Question
Chemistry:
Why are Triple Bond lengths shorter than Single and Double Bonds?
In Chemistry class we were told to hypothesize why we think bond lengths get shorter as multiple bonds increase, my question is, can someone explain it to me?I know that bond lengths in pecometers for C - C Single bonds is 154, in C - C Double bonds is 133, and 120 in C - C Triple bonds.
My assumption is that as more electrons become "shared" between the Carbon atoms, the orbitals become closer together. But why?
I know in the single bonds they are sp3, the double bond is sp2 and the triple bond is sp, does orbital shape have anything to do with why they are closer?
And I aslo know there are two pi bonds in the sp hybridized, C - C triple bonds, only one in the sp2 double bond and no pi bonds in the single bonded Carbon atoms. Does pi bonds havre anything to d with bond length?
I guess all this information just has me condused, maybe someone can set me straight?
Thnaks alot!
Answers (1)
by Timothy
There is an important electrostatic potential energy component to chemical bonding. When a bond forms, more electron density accumulates in the region between the positively charged nuclei than would be there if the electron "clouds" of the atoms just stayed the same as they are in isolated atoms. Since the electrons are negatively charged, when the probability of finding the electrons is greater in the region between the nuclei, the positively-charged nuclei are drawn together as they are attracted to the negatively charged electron density.
Thus, the electrons are the negatively charged "glue" that brings the positively charged nuclei together. In double and triple bonds, more electron density piles up in the region between the nuclei, so the nuclei are drawn together even more closely by their attraction to the electron density.
However, π bonds don't build up electron density directly between the nuclei, so π bonds don't add as much to the bond strength as σ bonds which do. π bonds shorten the bonds too, but their shortening effect is not as great as the effect of the σ bonds. Of course, π bonds always add to the effect of the σ bonds and therefore double bonds (σ + one π) and triple bonds (σ + two π) are stronger and shorter than single σ bonds alone.
Q: "I know in the single bonds they are sp³, the double bond is sp² and the triple bond is sp, does orbital shape have anything to do with why they are closer?"
A: Actually, yes. s orbitals are a little more contracted than p orbitals and the optimal distance between atoms for accumulating bonding electron density is consequently a little shorter when sp² hybrids are involved that when sp³ hybrids are involved; when sp hybrids are involved, the bonds a shortened a little bit more than when sp² hybrids are involved.
This small shortening can be seen by comparing the C–H bond distances in acetylene (H–C≡C–H, d(sp-CH) = 106 pm), ethylene (H₂C=CH₂, d(sp²-CH) = 108.7 pm) and ethane (H₃C–CH₃, d(sp³-CH) = 109.4 pm).
The differences in hybridization are less important than the difference due to bond order, however.
Full disclosure: This argument is fine as far as it goes, but there is also an important electronic kinetic energy contribution to bonding that requires a more sophisticated knowledge of the quantum mechanics of chemical bonds. I haven't attempted to explain that...
Source(s):
Chemistry professor
Chemistry:
Why are Triple Bond lengths shorter than Single and Double Bonds?
In Chemistry class we were told to hypothesize why we think bond lengths get shorter as multiple bonds increase, my question is, can someone explain it to me?I know that bond lengths in pecometers for C - C Single bonds is 154, in C - C Double bonds is 133, and 120 in C - C Triple bonds.
My assumption is that as more electrons become "shared" between the Carbon atoms, the orbitals become closer together. But why?
I know in the single bonds they are sp3, the double bond is sp2 and the triple bond is sp, does orbital shape have anything to do with why they are closer?
And I aslo know there are two pi bonds in the sp hybridized, C - C triple bonds, only one in the sp2 double bond and no pi bonds in the single bonded Carbon atoms. Does pi bonds havre anything to d with bond length?
I guess all this information just has me condused, maybe someone can set me straight?
Thnaks alot!
Answers (1)
by Timothy
There is an important electrostatic potential energy component to chemical bonding. When a bond forms, more electron density accumulates in the region between the positively charged nuclei than would be there if the electron "clouds" of the atoms just stayed the same as they are in isolated atoms. Since the electrons are negatively charged, when the probability of finding the electrons is greater in the region between the nuclei, the positively-charged nuclei are drawn together as they are attracted to the negatively charged electron density.
Thus, the electrons are the negatively charged "glue" that brings the positively charged nuclei together. In double and triple bonds, more electron density piles up in the region between the nuclei, so the nuclei are drawn together even more closely by their attraction to the electron density.
However, π bonds don't build up electron density directly between the nuclei, so π bonds don't add as much to the bond strength as σ bonds which do. π bonds shorten the bonds too, but their shortening effect is not as great as the effect of the σ bonds. Of course, π bonds always add to the effect of the σ bonds and therefore double bonds (σ + one π) and triple bonds (σ + two π) are stronger and shorter than single σ bonds alone.
Q: "I know in the single bonds they are sp³, the double bond is sp² and the triple bond is sp, does orbital shape have anything to do with why they are closer?"
A: Actually, yes. s orbitals are a little more contracted than p orbitals and the optimal distance between atoms for accumulating bonding electron density is consequently a little shorter when sp² hybrids are involved that when sp³ hybrids are involved; when sp hybrids are involved, the bonds a shortened a little bit more than when sp² hybrids are involved.
This small shortening can be seen by comparing the C–H bond distances in acetylene (H–C≡C–H, d(sp-CH) = 106 pm), ethylene (H₂C=CH₂, d(sp²-CH) = 108.7 pm) and ethane (H₃C–CH₃, d(sp³-CH) = 109.4 pm).
The differences in hybridization are less important than the difference due to bond order, however.
Full disclosure: This argument is fine as far as it goes, but there is also an important electronic kinetic energy contribution to bonding that requires a more sophisticated knowledge of the quantum mechanics of chemical bonds. I haven't attempted to explain that...
Source(s):
Chemistry professor
Saturday 22 August 2009
Half life
Resolved Question
Half life question...?
Hi, can someone give me a hand with this, i think i got the right idea, but it don't seem to give me the answer provided.
The radioactive isotope 51Cr is used to evaluate the lifetime of red blood cells.Its t½ = 27.7 days. A hospital laboratory has 80.0 mg of 51Cr. How much of 51Cr is left after 85 days?
Answer given = 9.6mg
by joeyeehu...
Best Answer - Chosen by Asker
All radioactive decay is a first order reaction.
First, you have to calculate the rate constant, k = 0.693/ t1/2
Therefore, k = 0.693 / 27.7
First order equation: ln Ao/A = kt
......................................ln 80/A = (0.693/27.7)(85)
Solving for A will give you the required answer.
Ao = initial mass
A = the mass after time,t
Half life question...?
Hi, can someone give me a hand with this, i think i got the right idea, but it don't seem to give me the answer provided.
The radioactive isotope 51Cr is used to evaluate the lifetime of red blood cells.Its t½ = 27.7 days. A hospital laboratory has 80.0 mg of 51Cr. How much of 51Cr is left after 85 days?
Answer given = 9.6mg
by joeyeehu...
Best Answer - Chosen by Asker
All radioactive decay is a first order reaction.
First, you have to calculate the rate constant, k = 0.693/ t1/2
Therefore, k = 0.693 / 27.7
First order equation: ln Ao/A = kt
......................................ln 80/A = (0.693/27.7)(85)
Solving for A will give you the required answer.
Ao = initial mass
A = the mass after time,t
Buffer solutions
Resolved Question
Which of the following canot function as a buffer solution:
HCN and KCN,
HF and NaF,
HNO3 and NaNO3,...?
HNO2 and NaNO2, or
NH3 and (NH4)2 SO4
by joeyeehu...
Best Answer - Chosen by Voters
In order to function as a buffer, it must have two components:
a) a weak acid and its conjugate base or
b) a weak base and its conjugate acid
HNO3 is a strong acid, therefore HNO3 and NaNO3 cannot function as a buffer.
The rest are buffer solutions.
Which of the following canot function as a buffer solution:
HCN and KCN,
HF and NaF,
HNO3 and NaNO3,...?
HNO2 and NaNO2, or
NH3 and (NH4)2 SO4
by joeyeehu...
Best Answer - Chosen by Voters
In order to function as a buffer, it must have two components:
a) a weak acid and its conjugate base or
b) a weak base and its conjugate acid
HNO3 is a strong acid, therefore HNO3 and NaNO3 cannot function as a buffer.
The rest are buffer solutions.
Resolved Question
Need Help With This Rate Equation Question?
Following rate equation was determined from reaction
NO2+CO=NO+CO2:
Rate=k[NO2][CO]
The following mechanism has been proposed:
NO2 + CO=ONOCO (slow)
ONOCO= NO+CO2 (fast)
Determine if this mechanism is consistent with rate equation?
I wasn't fully sure if I done this correct but since the first reaction in the mechanism is slow it's the rate determining step and so the rate must be Rate=k[NO2][CO].
Can someone confirm this or do I need more info?
by joeyeehu...
Best Answer - Chosen by Asker
You are right in saying that the slow step is the rate determining step and you can write the rate equation from it. But the question is whether the mechanism proposed is consistent with the rate equation?
To confirm this, just add the two elementary steps proposed. You will get the overall equation. This shows that the mechanism proposed is consistent with the rate equation.
ONOCO is called the intermediate and it will not feature in the overall equation. If you get the intermediate in the overall equation, then the mechanism proposed is not correct.
Need Help With This Rate Equation Question?
Following rate equation was determined from reaction
NO2+CO=NO+CO2:
Rate=k[NO2][CO]
The following mechanism has been proposed:
NO2 + CO=ONOCO (slow)
ONOCO= NO+CO2 (fast)
Determine if this mechanism is consistent with rate equation?
I wasn't fully sure if I done this correct but since the first reaction in the mechanism is slow it's the rate determining step and so the rate must be Rate=k[NO2][CO].
Can someone confirm this or do I need more info?
by joeyeehu...
Best Answer - Chosen by Asker
You are right in saying that the slow step is the rate determining step and you can write the rate equation from it. But the question is whether the mechanism proposed is consistent with the rate equation?
To confirm this, just add the two elementary steps proposed. You will get the overall equation. This shows that the mechanism proposed is consistent with the rate equation.
ONOCO is called the intermediate and it will not feature in the overall equation. If you get the intermediate in the overall equation, then the mechanism proposed is not correct.
Resolved Question
How we can find hybridization state of carbon in organic compounds?
eg CH2=C=CH2(all 1st 2nd & 3rd carbons)?
by joeyeehu...
Best Answer - Chosen by Asker
For carbon, to determine the types of hybridisation formed, all you have to do is to determine the number of atoms or groups that are attached to the carbon atom.
If the number is:
a) 2 --------------------> sp
b) 3 --------------------> sp2
c) 4 --------------------> sp3
So, the first carbon ----------> 3 -----------> sp2
..... the second carbon -----> 2 -----------> sp
......the third carbon ------------3 ------------> sp2
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How we can find hybridization state of carbon in organic compounds?
eg CH2=C=CH2(all 1st 2nd & 3rd carbons)?
by joeyeehu...
Best Answer - Chosen by Asker
For carbon, to determine the types of hybridisation formed, all you have to do is to determine the number of atoms or groups that are attached to the carbon atom.
If the number is:
a) 2 --------------------> sp
b) 3 --------------------> sp2
c) 4 --------------------> sp3
So, the first carbon ----------> 3 -----------> sp2
..... the second carbon -----> 2 -----------> sp
......the third carbon ------------3 ------------> sp2
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Friday 21 August 2009
Resolved Question
What are the H-C-C,CCC and HCH Bond angle in butane?
what about others? Like methane, ethane, propane.
by joeyeehu...
Best Answer - Chosen by Voters
The structural formula of butane is CH3CH2CH2CH3.
All the carbon atoms are bonded to 4 neighbouring atoms tetrahedrally.
Just imagine that you are the carbon atom and you are in the centre of a triangular based pyramid.
The four neighbouring atoms attached to you are at the four corners of the pyramid.
All the bond angles will be 109.5 degree.
The same applies to methane, ethane and propane.
What are the H-C-C,CCC and HCH Bond angle in butane?
what about others? Like methane, ethane, propane.
by joeyeehu...
Best Answer - Chosen by Voters
The structural formula of butane is CH3CH2CH2CH3.
All the carbon atoms are bonded to 4 neighbouring atoms tetrahedrally.
Just imagine that you are the carbon atom and you are in the centre of a triangular based pyramid.
The four neighbouring atoms attached to you are at the four corners of the pyramid.
All the bond angles will be 109.5 degree.
The same applies to methane, ethane and propane.
Thursday 20 August 2009
Resolved Question
Why H2O has bond angle 105 but H2S has only 91.5?
by joeyeehu...
Best Answer - Chosen by Asker
Both oxygen and sulphur are in Group 16.
There are two lone pair each in H2O as well as in H2S.
But oxygen is more electronegative than sulphur.
Hence, the bonding pair of electrons in O-H bonds are drawn closer to O.
These electrons experience greater repulsive force compared to that in H2S.
Therefore, the HOH angle is greater than HSH angle.
Asker's Comment:
this answer is more understandable with simple laguage so a student like me will like this answer more than others
Why H2O has bond angle 105 but H2S has only 91.5?
by joeyeehu...
Best Answer - Chosen by Asker
Both oxygen and sulphur are in Group 16.
There are two lone pair each in H2O as well as in H2S.
But oxygen is more electronegative than sulphur.
Hence, the bonding pair of electrons in O-H bonds are drawn closer to O.
These electrons experience greater repulsive force compared to that in H2S.
Therefore, the HOH angle is greater than HSH angle.
Asker's Comment:
this answer is more understandable with simple laguage so a student like me will like this answer more than others
Resolved Question
What's the ionic product of water, Kw?
by joeyeehu...
Best Answer - Chosen by Asker
Water dissociates slightly to form ionsH2O <==========> H+ + OH-
The equilibrium constant Kw = [H+] [OH-]
[H2O] is left out from the equation as its concentration is virtually constant. (due to high concentration compared to the concentration of ions).
At 25 degree C, [H+] = [OH-] = 1.0 x 10^-7
Hence, Kw = 1.0 x 10^-14
What's the ionic product of water, Kw?
by joeyeehu...
Best Answer - Chosen by Asker
Water dissociates slightly to form ionsH2O <==========> H+ + OH-
The equilibrium constant Kw = [H+] [OH-]
[H2O] is left out from the equation as its concentration is virtually constant. (due to high concentration compared to the concentration of ions).
At 25 degree C, [H+] = [OH-] = 1.0 x 10^-7
Hence, Kw = 1.0 x 10^-14
Resolved Question
Is Thymol blue a suitable indicator for the following titrations?
Is Thymol blue (pKa=8.9) suitable indicator for each of the following titrations?
a) 0.10M HCL versus 0.10M KOH
b) 0.10M CH3COOH versus 0.10M KOH?
c) 0.10M HNO3 versus 0.10m NH3?
by joeyeehu...
Best Answer - Chosen by Asker
The choice of an indicator depends on the pH when the equivalent point is achieved.
The pH when the equivalent point is achieved must coincide with the pH range of the indicator.
a) is a titration of strong acid and strong base.
The equivalent point occurs between pH 3 to 10.
b) is a weak acid and strong base. The equivalent point occurs between pH 7 to 13
c) is a strong acid and a weak base. The equivalent point occurs between pH 3 to 7.
Hence, thymol blue (pKa = 8.9) is suitable to be used in (a) and (b) as it will change colour when the equivalent point is reached.
(c) is not suitable because it wont change colour eventhough the equivalent point is reached,.
Is Thymol blue a suitable indicator for the following titrations?
Is Thymol blue (pKa=8.9) suitable indicator for each of the following titrations?
a) 0.10M HCL versus 0.10M KOH
b) 0.10M CH3COOH versus 0.10M KOH?
c) 0.10M HNO3 versus 0.10m NH3?
by joeyeehu...
Best Answer - Chosen by Asker
The choice of an indicator depends on the pH when the equivalent point is achieved.
The pH when the equivalent point is achieved must coincide with the pH range of the indicator.
a) is a titration of strong acid and strong base.
The equivalent point occurs between pH 3 to 10.
b) is a weak acid and strong base. The equivalent point occurs between pH 7 to 13
c) is a strong acid and a weak base. The equivalent point occurs between pH 3 to 7.
Hence, thymol blue (pKa = 8.9) is suitable to be used in (a) and (b) as it will change colour when the equivalent point is reached.
(c) is not suitable because it wont change colour eventhough the equivalent point is reached,.
2. Balance the redox equations by the ion-electron method:
Br2 --> Br2O3- + Br-(in basic solution)?
It is easier to balance equations in basic solution by first balancing them in acidic solution.
1. Break up the reaction into two half-reactions.Br2 -----> Br2O31-Br2 -----> Br1-
2. Balance the main atoms; in this case, BrBr2 -----> Br2O31-
(Br already balanced)Br2 -----> 2Br1-
3. Balance the O by adding H2OBr2 + 3H2O -----> Br2O31-Br2 -----> 2Br1-
4. Balance the H by adding H+Br2 + 3H2O -----> Br2O31- + 6H+Br2 -----> 2Br1-
5. Balance the charges by adding e- to the more positive sides of each half-reaction.
Br2 + 3H2O -----> Br2O31- + 6H+ + 5e- (oxidation)Br2 + 2e- -----> 2Br1- (reduction)
6. Make the e- gained and lost equal. Multiply the top equation by 2 and the bottom one
by 5.2Br2 + 6H2O -----> 2Br2O31- + 12H+ + 10e-5Br2 + 10e- -----> 10Br1-
7. Add the two half-reactions.7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H+
The equation is balanced for an acidic solution.
8. To convert the equation to a basic solution, add the same number of OH- to each side of the
equation as there are H+.12OH- + 7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H+ + 12OH-
9. Combine the H+ and OH- to make water.
12OH- + 7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H20
10. Simplify the H2O12OH- + 7Br2 -----> 2Br2O31- + 10Br1- + 6H20
The equation is balanced for a basic solution. Note that both sides are -12 in charge and that
all atoms are balanced.
Br2 --> Br2O3- + Br-(in basic solution)?
It is easier to balance equations in basic solution by first balancing them in acidic solution.
1. Break up the reaction into two half-reactions.Br2 -----> Br2O31-Br2 -----> Br1-
2. Balance the main atoms; in this case, BrBr2 -----> Br2O31-
(Br already balanced)Br2 -----> 2Br1-
3. Balance the O by adding H2OBr2 + 3H2O -----> Br2O31-Br2 -----> 2Br1-
4. Balance the H by adding H+Br2 + 3H2O -----> Br2O31- + 6H+Br2 -----> 2Br1-
5. Balance the charges by adding e- to the more positive sides of each half-reaction.
Br2 + 3H2O -----> Br2O31- + 6H+ + 5e- (oxidation)Br2 + 2e- -----> 2Br1- (reduction)
6. Make the e- gained and lost equal. Multiply the top equation by 2 and the bottom one
by 5.2Br2 + 6H2O -----> 2Br2O31- + 12H+ + 10e-5Br2 + 10e- -----> 10Br1-
7. Add the two half-reactions.7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H+
The equation is balanced for an acidic solution.
8. To convert the equation to a basic solution, add the same number of OH- to each side of the
equation as there are H+.12OH- + 7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H+ + 12OH-
9. Combine the H+ and OH- to make water.
12OH- + 7Br2 + 6H2O -----> 2Br2O31- + 10Br1- + 12H20
10. Simplify the H2O12OH- + 7Br2 -----> 2Br2O31- + 10Br1- + 6H20
The equation is balanced for a basic solution. Note that both sides are -12 in charge and that
all atoms are balanced.
Tuesday 11 August 2009
Resolved Question
Calculate Ksp from titration experiment???10 points?
0.025L of Solution A [ Ca(OH)2 with 0.0125M of NaOH]...titrated against 0.0120L of HCl. [HCl] =0.1034
To break it down...
FIND: [OH-] from titration[OH-] from NaOH
[OH-] from Ca (OH)2 (by subtraction)[Ca2+]
Solubility of Ca(OH)2 in molL-1Ksp
by joeyeehu...
Best Answer - Chosen by Asker
No. of moles of HCl = 0.1034 x 0.0120 = 1.2408 x 10^-3 mol
That means total no. of moles of OH- = 1.2408 x 10^-3 mol
No. of moles of OH- from NaOH = 0.0125 x 0.025 = 3.125 x 10^-4
ThereforeNo. of moles of OH- from Ca(OH)2 = 1.2408 x 10^-3 - 3.125 x 10^-4= 9.283 x 10^-4
mol
Volume of solution A is 0.025L
Hence, [OH-] from Ca(OH)2 = 9.283 x 10^-4/ 0.025 M= 0.037132 M
[Ca2+] = 0.037132/2
Ksp = [Ca2+] [OH-]^2. = ( 0.037132) X { 0.037132/2 }^2. = 1.28 x 10^-5
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thanks
Calculate Ksp from titration experiment???10 points?
0.025L of Solution A [ Ca(OH)2 with 0.0125M of NaOH]...titrated against 0.0120L of HCl. [HCl] =0.1034
To break it down...
FIND: [OH-] from titration[OH-] from NaOH
[OH-] from Ca (OH)2 (by subtraction)[Ca2+]
Solubility of Ca(OH)2 in molL-1Ksp
by joeyeehu...
Best Answer - Chosen by Asker
No. of moles of HCl = 0.1034 x 0.0120 = 1.2408 x 10^-3 mol
That means total no. of moles of OH- = 1.2408 x 10^-3 mol
No. of moles of OH- from NaOH = 0.0125 x 0.025 = 3.125 x 10^-4
ThereforeNo. of moles of OH- from Ca(OH)2 = 1.2408 x 10^-3 - 3.125 x 10^-4= 9.283 x 10^-4
mol
Volume of solution A is 0.025L
Hence, [OH-] from Ca(OH)2 = 9.283 x 10^-4/ 0.025 M= 0.037132 M
[Ca2+] = 0.037132/2
Ksp = [Ca2+] [OH-]^2. = ( 0.037132) X { 0.037132/2 }^2. = 1.28 x 10^-5
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thanks
Resolved Question
Chemistry question- general organic?
Explanation of inductive effect and how it effects acidic behaviour??
by joeyeehu...
Best Answer - Chosen by Asker
Inductive effect can be divided into two types, positive inductive and negative inductive.A group or atom is said to have a positive inductive effect if it tends to push away electrons away from them(electron donating group). I will increase the electron charge density of its neighbour. Example of such group is the alkyl group ( CH3, C2H5 ).Electron withdrawing group will attract the electrons toward itself (negative inductive effect), ex. F, Cl, NO2. They will reduce the electron charge density of the O--H bond. This will weaken the O--H bond and the molecule is able to donate the H+ more easily. It increases acidic behaviour. ( acid is a proton(H+) donor )
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Chemistry question- general organic?
Explanation of inductive effect and how it effects acidic behaviour??
by joeyeehu...
Best Answer - Chosen by Asker
Inductive effect can be divided into two types, positive inductive and negative inductive.A group or atom is said to have a positive inductive effect if it tends to push away electrons away from them(electron donating group). I will increase the electron charge density of its neighbour. Example of such group is the alkyl group ( CH3, C2H5 ).Electron withdrawing group will attract the electrons toward itself (negative inductive effect), ex. F, Cl, NO2. They will reduce the electron charge density of the O--H bond. This will weaken the O--H bond and the molecule is able to donate the H+ more easily. It increases acidic behaviour. ( acid is a proton(H+) donor )
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Wednesday 17 June 2009
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