3.091 Introduction to Solid-State Chemistry - Fall 2012

Problem Set 11

Problem set quiz will not be scheduled for this homework set

Problem 1

Silver sulfate dissolves in water according to the following reaction:

Ag2SO4 ⇌ 2 Ag+ (aq) + SO42-(aq)

for which the value of the solubility product, Ksp is 1.4 x 10-5.

(a) Calculate the solubility of Ag2SO4 in water. Express your answer in moles Ag2SO4/liter

solution.

(b) Calculate the solubility of Ag2SO4 in 1.00 M Na2SO4(aq). Express your answer in moles

Ag2SO4/liter solution. Assume that Na2SO4(aq) is fully dissociated.

Problem 2

(a) The solubility of bismuth iodide (BiI3) in water is 3.091 x 10-3 M. Calculate the value of

the solubility product. The dissolution products are Bi3+(aq) and I- (aq).

(b) Do you expect the solubility of BiI3 in 0.1 M NaCl(aq) to be equal to, greater than, or less

than that of BiI3 in water? Explain.

Problem 3

Silver arsenate (Ag3AsO4) dissolves in water according to

Ag3AsO4 = 3 Ag+(aq) + AsO43-(aq) Ksp = 1.1 x 10-22 at 25°C

Calculate the solubility of silver arsenate in 0.001 1 M AgNO3. Express your answer in moles of

Ag3AsO4 per liter of solution.

Problem 4

(a) Magnesium phosphate dissolves in water according to

Mg3(PO4)2 = 3 Mg2+(aq) + 2 PO43-(aq) Ksp = 1.11 x 10-25 at 25°C

Calculate the solubility of magnesium phosphate (Mg3(PO4)2) in pure water. Express

your answer in moles Mg3(PO4)2 per liter of solution (M).

(b) Calculate the solubility of magnesium phosphate (Mg3(PO4)2) in a 4.44 x 10-3 M

magnesium carbonate (MgCO3) solution. Express your answer in moles Mg3(PO4)2 per

liter of solution (M).

Problem 5

(a) Lead chloride dissolves in water according to

PbCl2(s) = Pb2+ (aq) + 2 Cl- (aq)

The solubility in pure water has been measured to be 4.44 g L-1. Calculate the solubility

product of lead chloride in pure water.

(b) Calculate the solubility of lead chloride in a 3.091 x 10-4 M potassium chloride (KCl)

solution. Express your answer in moles PbCl2 per liter of solution (M). Regardless of

what answer you obtained in part (a), in this calculation use the value of 3.091 x 10-5 for

Ksp of lead chloride.

Problem 6

The following information is available from cooling experiments for the binary system

Cu-Ni:

T(°C) Melt composition (atomic %

Ni)

Composition of solid first

formed on cooling (atomic

% Ni)

1100 3 10

1180 20 37

1260 40 57

1340 60 73

1410 80 87

(a) Construct the T/composition diagram from these data and information provided in the

Periodic Table.

(b) For the following temperatures and compositions, what are the phases present and what

are their respective compositions?

T(°C) Composition (atomic

% Ni)

Phase Composition (atomic

% Ni)

1120 15

1200 55

1300 60

Problem 7

Given the triple point of copper (Cu) and data provided in the Periodic Table, sketch a

reasonable P/T equilibrium phase diagram for copper.

Triple point: TT = 1080°C

PT = 6.1 x 10-6 atm

Problem 8

Draw schematic phase diagrams for binary systems with (a) complete liquid and solid

solubility, (b) complete liquid but zero solid solubility, and (c) complete liquid and limited solid

solubility. (In your sketches label phase fields and give characteristic temperatures.)

Problem 9

The “triple point” of H2O is at 0.006 atm and 0.01°C; knowing in addition the boiling and

freezing point temperatures of H2O at 1 atm pressure:

(a) Draw a schematic phase diagram for H2O.

(b) Give the reasoning behind this statement: The diagram permits the conclusion that ice

will most likely float on water!

Problem 10

Given the “triple point” of copper (Cu) and data provided in the Period Table, sketch a

reasonable P/T equilibrium phase diagram for Cu.

(Triple point, TT = 1080°C; PT = 6.1 x 10-6 atm)

Problem 11

Given the schematic A-B binary phase diagram below:

(a) Label all phase regions on the schematic phase diagram.

(b) Draw a schematic cooling curve for a binary melt of 70 at.% B + 30 at.% A.

Label characteristics temperatures and indicate the phases present in the various

temperature regions.

(c) What are the phases present and their compositions if the melt considered in (b) is

cooled to T = 600°C?

(d) What fraction of the melt considered in (b) is solidified at the temperature of 550°C?

Problem 12

a) Shown below is the Mg-Si phase diagram. Note that a magnified version of the Mg rich

portion of the diagram is shown on the right. Label each region of the diagram

(including the magnified portion).

b) Why do Mg and Si exhibit limited solubility in one another?

c) Calculate the relative amount of each phase at room temperature in a sample with

overall composition 0.80 mole fraction Si.

Problem 13

Naphthalene melts at 80⁰ C and benzene melts at 5⁰ C. The two materials form a completely

miscible liquid at high temperature but have very little miscibility in the solid state. The

following cooling curves are observed for various liquid compositions of naphthalene and

benzene (X stands for mole fraction benzene). Draw the simplest phase diagram in the space

provided that is consistent with the cooling curve data. Label each section of each cooling curve

to indicate what phases are present.

Problem 14

The solubility of benzalphthalide in various solvents has been shown to be a function of their

solubility parameter. This relationship is shown below.

benzalphthalide

Solvents( from left to right): dimethicone, octane, MIBK, ethyl acetate,

acetone, benzaldehyde, acetonitrile, benzyl alcohol, propylene carbonate

a) Hypothesize why the solubility goes through a maximum.

b) Estimate what the solubility parameter of benzalphthalide

0

5

10

15

20

25

30

35

40

5 7 9 11 13 15

solu

bili

ty (%

)

solubility parameter of solvent

solubility of benzalphthalide in various solvents