Question

# Can you please check my answers and tell me if they are correct? thanks 8. Write...

Can you please check my answers and tell me if they are correct? thanks

8. Write the ionic equation for dissolution and the solubility product (Ksp) expression for each of the following slightly soluble ionic compounds:

(a) PbCl2       PbCl2(s) --> Pb2+(aq) + 2Cl-(aq)                           Ksp = [Pb2+][Cl-]2

(b) Ag2S        Ag2S(s) --> 2Ag+(aq) + S2-(aq)                             Ksp =[Ag+]2[S2-]

(c) Sr3(PO4)2 Sr3(PO4)2(s) --> 3Sr2+(aq) + 2PO43-(aq)         Ksp =[Sr2+]3[PO43-]2

(d) SrSO4       SrSO4(s) --> Sr2+(aq) + SO42-(aq)                       Ksp =[Sr2+][SO42-]

14. Assuming that no equilibria other than dissolution are involved, calculate the molar solubility of each of the

following from its solubility product:

(a) Ag2SO4

The solubility product of Ag2SO4 is Ksp = 1.4 x 10-5

Ksp =[Ag+]2[SO42-]

Solubility, S is equal to [SO42-], so [Ag+] = 2S

Therefore, 1.5 x 10-5 = (2S)2 x S = 4S3

S = 0.01554 mol/L

(b) PbBr2

Ksp = 4.0×10–5

Ksp = [Pb2+][Br-]2

S = [Pb2+]

[Br-] = 2S

4.0 x 10-5 = S x (2S)2 = 4S3

S = 0.02154 mol/L

(c) AgI

Ksp = 8.5×10–17

Ksp = [Ag+][I-]

S = [Ag+] = [I-] = Ksp1/2

S = 9.22 x 10-9 mol/L

(d) CaC2O4∙H2O

Ksp = 2.7×10–9

Ksp = [Ca2+][C2O42-]

S = [Ca2+] = [C2O42-] = Ksp1/2

S = 5.20 x 10-5 mol/L

28. The following concentrations are found in mixtures of ions in equilibrium with slightly soluble solids. From the concentrations given, calculate Ksp for each of the slightly soluble solids indicated:

(a) AgBr: [Ag+] = 5.7 × 10–7 M, [Br–] = 5.7 × 10–7 M

Ksp = [Ag+][Br] = 5.7 × 10–7 M x 5.7 × 10–7 M = 3.25 x 10-13

(b) CaCO3: [Ca2+] = 5.3 × 10–3 M, [CO3 2−] = 9.0 × 10–7 M

Ksp = [Ca2+][CO3 2−] = 4.77 x 10-9

(c) PbF2: [Pb2+] = 2.1 × 10–3 M, [F–] = 4.2 × 10–3 M

Ksp = [Pb2+][F]2 = 3.70 x 10-8

(d) Ag2CrO4: [Ag+] = 5.3 × 10–5 M, 3.2 × 10–3 M

Ksp = [Ag+]2[CrO42-] = 8.99 x 10-12

(e) InF3: [In3+] = 2.3 × 10–3 M, [F–] = 7.0 × 10–3 M

Ksp = [In3+][F]3 = 7.89 x 10-10

54. Calculate the molar solubility of AgBr in 0.035 M NaBr (Ksp = 5 × 10–13).

[Br-] = 0.035 M

[Ag+] = Ksp/[Br-] = 5 × 10-13/0.035 M = 1.43 x 10-11 M

Chapter 16

4. A helium-filled balloon spontaneously deflates overnight as He atoms diffuse through the wall of the balloon. Describe the redistribution of matter and/or energy that accompanies this process.

Due to this energy the helium atoms in the balloon are in constant collisions with the walls of the balloon from where they eventually find a way through the walls and start deflating out and disperse themselves in the environment till they form a uniform mixture.

12. Arrange the following sets of systems in order of increasing entropy. Assume one mole of each substance and the same temperature for each member of a set.

(a) H2(g), HBrO4(g), HBr(g) H2(g), HBr(g), HBrO4(g)

(b) H2O(l), H2O(g), H2O(s) H2O(s), H2O(l), H2O(g)

(c) He(g), Cl2(g), P4(g)          He(g), Cl2(g), P4(g)

16. Predict the sign of the entropy change for the following processes.

(a) An ice cube is warmed to near its melting point. The sign of the entropy will be positive, this is because increase in temperature increases randomness or disorder in a system.

(b) Exhaled breath forms fog on a cold morning. The entropy will be negative. The air at the outside/surrounding is cooler that the air breathed out therefore, the cooler air in the surrounding will decrease the temperature of the breathed air which will increase order in the breathed air hence decrease in entropy.

(c) Snow melts. When the snow melts it tends to release the compacted molecules which become more random, This increases entropy or disorder. The sign will be positive.

24. “Thermite” reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is Fe2 O3(s) + 2Al(s) ⟶ Al2 O3(s) + 2Fe(s). Is the reaction spontaneous at room

temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.

dG = dH - T* dS

dS = dq/T

dS = -851.8 kJmol-1/298 K

dS = - 2.858

dG = -851.8 - (-2.858 * 298)

dG = 0

hence the reaction is at equilibrium at standard conditions and not spontaneous.

Hi you did very good job, only one mistake i have observed, otherwise this is 99.9999999% perfect.

14(a) is wrong. Given The solubility product of Ag2SO4 is Ksp = 1.4 x 10-5 , but you used 1.5 x 10-5

Therefore, 1.5 x 10-5 = (2S)2 x S = 4S3

S = 0.01554 mol/L

For 54 i do not have sufficient time to check.

Chapter 16:

4. Answer: Diffusion is the process by which molecules move from a region of high concentration to a region of low concentration. This movement is due to kinetic energy possessed by molecules.

Add the above sentence before "Due to this energy paragraph.........................................."

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