What is the molar solubility of Cu(OH)2, Ksp=6.0 x 10^-10?

joeyeehu...

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Cu(OH)2 ---------------------> Cu2+ + 2OH-

First you let the molar solubility to be x.
therefore the conc of Cu2+ = x
and the conc of OH- = 2x

Ksp = [Cu2+] [OH-]^2

........ = (x) (2x)^2
........ = 4x^3

Hence 4x^3 = 6.0 x 10^-10

x = 5.31 x 10^-4

AgNO3(aq) is slowly added to a solution that is 0.280 M NaCl and also 0.0027 M KBr?

What is [Ag]+ at the point at which the second anion begins to precipitate?

joeyeehu...

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This is a solubility product questions.

You must compare the Ksp of AgCl and that of AgBr.

The Ksp of AgCl > the Ksp of AgBr
This means AgCl is more soluble than AgBr.
The AgBr will precipitate first follower by the AgCl.

You will have to calculate the [Ag+] that will initiate the precipitation of AgCl.

[Ag+] [NaCl] = Ksp of AgCl
[Ag+] (0.28) = 1.0 x 10^-10
[Ag+] = 3.57 x 10^-10

Can someone help me with this chemistry problem?

61.20g of water at 58.0 degrees C is added to a student calorimeter containing 48.80g of water at 25.0 degrees C. What is the final temperature of the water mixture?

joeyeehu...

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When the water is mixed, the heat energy lost by the hotter water equals to the heat energy gain by the colder water.

Let the final temperature of the water mixture be t.
Heat lost = 61.20 x c x (58 - t)
Heat gain = 48.8 x c x (t - 25)

61.20 x c x (58 - t) = 48.8 x c x (t - 25)
3549.6 - 61.20t = 48.80t - 1220
110t = 4769.6
t = 43.36 degree C

Organic chem which componds with exhibit hydrogen bonding for intermolecular forces?

I don't understand how to determine this

1.ch3ch2F
2.ch3ch2Och3
3.ch3Nch3ch3
4.ch3ch2ch2ch3
5.ch3ch2ch2nh2

joeyeehu...

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Hydrogen bond is the electrostatic force of attraction between a hydrogen atom covalently bonded to a very electronegative atom ( nitrogen or oxygen or fluorine ) and another very electronegative atom ( N, O or F) of another molecule.

To determine the hydrogen bond,
1) Identify the presence of N, O or F in the molecule.
2) Determine whether there is a hydrogen atom directly attached to N, O or F

If the answers to 1) & 2) are YES, then it can form hydrogen bond.

1. There is no hydrogen atom directly attached to F
2. There is no hydrogen atom directly attached to O
3. There is no hydrogen atom directly attached to N
4. There is no N, O or F
5. The answers to 1) and 2) are YES. So............

Galvanic cells how to work out the cell potential using reduction potentials?

A galvanic cell is set up with a copper electrode in contact with CuSO4(aq) and a lead electrode in contact with Pb(NO3)2(aq), respectively, at 25ºC.

The standard reduction potentials are:

Pb2+ + 2 e- → Pb Eº= -0.13 V
Cu2+ + 2 e- → Cu Eº= +0.34 V


If the concentrations of Pb2+ and Cu2+ are each 1.0 M, what is the cell potential in Volt?

joeyeehu...

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First you need to identify the anode and cathode of the cell.

The anode is the half-cell with the standard reduction potential which is more negative. So, Pb half cell is the anode and oxidation will occur at anode.

The copper half cell which is more positive in SRP is the cathode.

Since the concentrations of Pb2+ and Cu2+ are 1.0M, use this formula to calculate the cell potential:

Cell potential = E(cathode) - E(anode)
.................. = (+0.34) - ( - 0.13)
.................. = 0,47 V

Calculate the concentration of silver ions in a saturated solution of silver chloride...........confusing?

Calculate the concentration of silver ions (in μmol/L) in a saturated solution of silver chloride AgCl (Ksp= 1.6 x 10-10)

joeyeehu...

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AgCl(s) <=====> Ag+(aq) + Cl-(aq)

Let the conc. of Ag+ = conc. of Cl- = x

Ksp = [Ag+] [Cl-] = (x) x (x) = x^2 = 1.6x 10^-10

x = 1.26 x 10^-5 mol L-1
.. = 12.6 umol / L

Use the phase diagram of water to explain?

why ice at the bottom of a glacier can melt when the rest of the glacier which is the same temperature remains solid.

joeyeehu...

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You are right.
If you look at the phase diagram of water, you will notice that the melting point curve slants to the left. It has a negative gradient. This means that the melting point of water decreases as the pressure is increase. At the bottom of glacier, it experiences a greater pressure, hence its melting point decreases. This means that it will only become ice at a lower temperature. At that temperature, the liquid water is more stable, hence it melts.In your phase diagram, you just draw a vertical line upward(increase in pressure) from the melting point curve and you will be in the liquid region of the phase diagram.

Why is it that only a few drops of indicators are used for an acid-base titration?

Is it something to do with the indicator being able to change the pH of the solution itself if too much is added, or perhaps it cannot accurately tell the end point once too much is added?

joeyeehu...

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Indicator itself is a weak acid or a weak base.

Adding too much of indicator will influence the pH of the solution and hence will not be able to change colour at the end point.

That's why only two drops of indicator are usually used.

What are the approximate bond angles?

CCl4

BCL3

CF4

SF2

NI3

CCl2F2

joeyeehu...

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CCl4, CF4 and CCl2F2 come under the same category. The carbon atom is surrounded by four electron pairs and all the electron pairs are the bonding pairs. Therefore they have the tetrahedral shapes with the approximate bond angles of 109.5 degree.

For NI3, the nitrogen atom is surrounded by four electron pairs but there are three bonding pairs and one lone pair. Therefore, the shape of NI3 is trigonal pyramidal. The repulsive force between lone pair - bond pair is greater than the bond pair - bond pair. Hence the bond angle is slightly smaller than 109.5. The approximate bond angle is about 107 degree.

For SF2, the sulphur atom is surrounded by four electron pairs but there are two bonding pairs and two lone pairs. Therefore, the shape of SF2 is ' V ' . The repulsive force between lone pair - lone pair is greater than between the lone pair - bond pair . Hence the bond angle is even smaller than 107. The approximate bond angle is about 104.5 degree.

For BCl3, the boron atom is surrounded by three electron pairs and the three electron pairs are all bonding pairs. Therefore the shape of BCl3 is trigonal planar and the bond angle is 120 degree.

Order of reaction question?

for the reaction 2NOBr(g)----->2NO(g) +Br2(g), the rate of equation is -d[NOBr]/dt =k[NOBr]^2. the overall rate reaction =


how do you go about doing this question? my answer appears to be wrong....I have a choice of 1,-1,2 and 0.5

joeyeehu...

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When you are given a rate equation, you can easily tell the overall order of reaction.

lets the rate equation be
rate = k [X] [Y]^2 [Z]^3

We can conclude that:
1) The order of reaction with respect to (wrt) X is 1( because the equation shows that the concentration of X is raised to power 1)
2) The order of reaction wrt Y is 2.
3) The order of reaction wrt Z is 3

4) The overall order of reaction is 1 + 2 + 3 = 6

So, the answer to your question is 2.

Help with this tough AP Chemistry Problem?

N2(g)  +  2O2(g)  <-->  N2O4(g)

If the value of the equilibrium constant with regard to pressure (Kp) is found to be 1.5 at 15°C, what is the value of the eqilibrium constant with regard to concentration?
(R = 0.0821 L•atm/(mol•K))



a. 8.4 x 102
b. 2.3
c. 9.4 x 107
d. 2.7 x 10–3

joeyeehu...

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Assume that the unit of Kp is atm-2.

Kp = Kc ( RT) ^ -2

Substitute the values into the equation, (a) is the answer.

T= 15 + 273 K
-2 is the number of moles of the products minus the number of moles of ractants. ( 1 - 3 = -2 )

AS CHEMISTRY HELP!!!!!!!!!!!!!!!?

1) In order to obtain a mass spectrum of a gaseous sample of chromium, the sample must first be ionised.

(i) give to reasons why it is necessary to ionise the cromium in the sample.

(ii) State what is adjusted so that each of the isotopes of chromium can be detected in turn.

(iii) Explain how the adjustment given in part (ii) enables the isotopes of chromium to be separated.

joeyeehu...

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1) The chromium atom must be ionised to form Cr+ so that it can be accelerated towards the negative plates and deflected by the magnetic field onto the detector so that a mass spectrum can be produced.

Positive ion will be attracted towards the negatively charged plates and charged ion can be deflected by the magnetic field.

2) The strength of the magnetic field is adjusted.

3)The angle of deflection of ion is proportional to the charge of ion and is inversely proportional to the mass of ion. That means lighter ion is deflected more compared to heavier ion.

By having a lower strength of magnetic field, the lighter ion is directed onto the detector first. As the strength of the magnetic field is increased, the heavier ion in turn is directed onto the detector until all the ions with different masses are detected and a mass spectrum is produced.

Rate Constant Chemistry?

What is the rate constant for a second order reaction when the initial [A] = 0.20M, the initial [B] = 0.86M and the initial rate = 0.0900 M/s?

joeyeehu...

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For the second order reaction, the rate equation is

rate = k [A] [B]
substitute the values given,

0.09 = k( 0.2) ( 0.86 )

solve for k.

n which do you overcome dipole-dipole forces?

In which do you overcome dipole-dipole forces?

1) Decomposing water into H2 and O2.

2) Evaporating PCl3.

3) Subliming solid C10H8.

4) Melting propane.

joeyeehu...

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2) Evaporating PCl3.

Evaporating PCl3 will make sure that the PCl3 molecules are far apart. This will make the dipole-dipole forces insignificant.

Dipole-dipole forces only take place if the molecules are polar. PCl3 is polar but the others are non-polar

What is the overall order of the reaction and the order with respect to [O3]?

Consider the reaction

2O3(g)    ->    3O2(g)

rate =  k[O3]^2 [O2]^−1 .
What is the overall order of the reaction and the order with respect to [O3]?

there are answer choices:
1. −1 and 3
2. 0 and 1
3. 1 and 2
4. 3 and 2
5. 2 and 2

Please explain how to do it too, I need to know how to work it out.

joeyeehu...

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When you are given a rate equation, let say

rate = k [A]^x [B]^y [C]^z

we can say that the order of reaction with respect to (wrt) A is x.
The order of reaction wrt B is y and
the order of reaction wrt C is z.

The overall order of reaction is x + y + z

So, the answer to your question is obvious.
It is 3) 1 and 2

overall order is 2 + (-1) = 1

What is the relationship between structure and Rf value?

joeyeehu...

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Rf stands for the retention factor in chromatography. It is a measure of how strongly the substituents are attached (adsorp) to the stationary phase. The stronger the adsorption, the lower is the Rf value.

By the way, Rf can be calculated by dividing the distance covered by the substituent with distance covered by the mobile phase.

A bulky structure ( branched isomer) has a weaker bond compared to a straight chained isomer. This is because the area of contact betweeen molecules is less compared to the straight chained isomer. ( van der Waal forces) Hence it moves faster and have a higher Rf value

If the substituent can form hydrogen bond with the stationary phase, then its Rf value will be lower as the strong hydrogen bond will cause the substituent to move at a slower pace along the stationary column.

How do I determine which molecules are polar?

I am given CCl4, CH4, H3C-CH2-CH2-CH2-CH2- CH3, H2O, CO2, and O2

joeyeehu...

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To determine the polarity of a molecule, you need to know two things.

a) Determine whether the bonds are polar?
b) Determine whether the molecule is symmetrical.(shapea)

A polar molecule must have polar bond and the molecule must be assymmetrical (not symmetrical).

A polar bond is formed if the atoms are of different electronegativities.

a) CCl4 -----> polar bond but symmetrical---> non polar
b) CH4 -----> polar bond but symmetrical---> non polar
c) same as above
d) H2O -----> polar bond and assymmetrical (V-shaped)--> polar molecule
e) CO2 -----> polar bond but linear in shape (symmetrical) ----> non polar
f) O2 --------> non polar bond-----------------------> non polar

What is the rate law of the following mechanism:?

E  +  S   <- ->   ES       (fast)
   ES         ->  E + P    (slow)

E is enzyme, S is substrate, P is product.

joeyeehu...

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let the rate constant of the forward reaction be k1;
let the rate constant of the backward reaction be k2;
let the rate constant of the forward reaction of the second eq be k3

For the first reversible equation:(fast)
forward reaction: rate = k1 [E][S]
backward reaction: rate = k2 [ES]

At equilibrium, rate of forward reaction = rate of backward reaction
k1[E][S] =k2[ES]

[ES] = { k1[E][S] } / k2 ......................(1)

For the slow reaction:

rate = k3 [ES]...................................(2)

Substitute (1) into (2)

rate = (k3) { k1[E][S] } / k2

rate = k [E] [S] ; where k = (k3)(k1) / k2