mrstorie.wikispaces.com 40S Chemistry Student – EquilibriumUnit

Equilibrium

EQUILIBRIUM OUTCOMES

All important vocabulary is in Italics and bold.

C12-4-01:Relate the concept of equilibrium to physical and chemical systems.

Include: conditions necessary to achieve equilibrium.

C12-4-04:Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.

Include: ICE tables.

C12-4-03:Use the value of the reaction quotient, Qto explain how far a system at equilibrium has gone towards completion.

C12-4-11:Write solubility product (Ksp) expressions from balanced chemical equations for salts with low solubility and solve related problems.

C12-4-06:Use Le Chatelier’s principle to predict and explain shifts in equilibrium.

Include: Interpret concentration versus time graphs.

C12-4-09 Describe some practical applications of Le Chatelier’s principle.

Additional KEY Terms

Closed systemMacroscopicDissociation

SaturatedIonization

EQUILIBRIUM EXPRESSIONS AND THE CONSTANT

C12-4-01:Relate the concept of equilibrium to physical and chemical systems.

  1. Write the equilibrium expressions (mass action expression) for each of the following reactions:

  1. SO2(g) + NO2(g) SO3(g) + NO(g)
/
  1. 2 C(s) + 3 H2(g) C2H6(g)

  1. 3 O2(g) 2 O3(g)
/
  1. MgCO3(s) CO2(g) + 2 MgO(s)

  1. 2 Bi3+(aq) + 3 H2S(g) 2 Bi2S3(s) + 6 H+(aq)
/
  1. I2(aq) I2(s)

  1. Cl2(g) + PCl3(g) PCl5(g)
/
  1. I2(g) + Cl2(g) 2 ICl(g)

  1. 2 NO2(g) 2 NO(g) + O2(g)
/
  1. 2 SO2(g) + O2 (g) 2 SO3(g)

  1. Cl2(g) + PCl3(s) PCl5(g)

  1. Comment on the favorability of product formation in each of the reactions.
  1. H2(g) + F2(g) 2 HF(g) KC = 1.0 ×1013
  1. SO2(g) + NO2(g) NO(g) + SO3(g) KC = 1.0 ×102
  1. 2 H2O(g) 2 H2(g) + O2(g) KC = 6.0 ×10–28
  1. Chemists have determined the equilibrium constants for several reactions. In which of these reactions are the products favoured over the reactants?
  1. KC = 1.0×102
  1. KC = 3.5
  1. KC = 0.003
  1. KC = 6.0 ×10–4
  1. Give an example of physical equilibrium you encounter in daily life and explain it briefly.
  1. What are the conditions necessary for a system to reach equilibrium and what signs are there that equilibrium has been reached?

EQUILIBRIUM EXPRESSIONS AND THE CONSTANT (TYPE I AND II)______

C12-4-04:Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.

  1. The formation of ammonia from hydrogen and nitrogen occurs by the reactionbelow:

3 H2 (g) + N2 (g) ↔ 2 NH3 (g)

Analysis of an equilibrium mixture of nitrogen, hydrogen, and ammonia contained ina 1.00 L flask at 300.0°C gives the following results: hydrogen 0.150 moles; nitrogen0.250 moles: ammonia 0.100 moles. Calculate KC for the reaction. (11.9)

  1. A mixture at equilibrium at 827°C contains 0.552 moles of CO2, 0.552 moles H2,0.448 moles CO, and 0.448 moles of H2O in a 1.00 L container. What is the Kcconstant? (0.659)

CO2 (g) + H2 (g) ↔ CO (g) + H2O (g)

  1. The equilibrium constant for the reaction at 755°C is 0.256.

4 H2 (g) + CS2 (g) ↔ CH4 (g) + 2 H2S (g)

What is the equilibrium concentration of H2S if at equilibrium [CH4] = 0.00108 mol/L, [H2] = 0.316 mol/L, [CS2] = 0.0898 mol/L? (0.461)

  1. Find the value of K if at equilibrium there is 25.0 moles of P4, 10.0 moles of H2and 5.00 moles of PH3, in a 5.00 L container. The equation is (0.00313)

P4 (g) + 6 H2 (g) ↔ 4 PH3 (g)

  1. Find the value of K for the equilibrium system

ZnO (s) + CO (g) ↔ Zn (s) + CO2 (g)

If at equilibrium there are 3.0 moles of CO, 4.0 moles of Zn and 4.0 moles of CO2in a 500.0 mL container. (1.3)

  1. If K = 46.0 forH2 (g) + I2 (g) ↔ 2 HI (g)

What [I2] would be in equilibrium with 0.50 mol/L HI and 0.10 mol/L H2? (0.054)

  1. If K = 10.0 forN2 (g) + 3 H2 (g) ↔ 2 NH3 (g)

How many moles of NH3, at equilibrium, will be in a 2.00 L container if[H2] is 0.600 mol/L and [N2] is 0.100 mol/L? (0.930)

  1. Ammonia is produced according:3 H2(g) + N2(g)  2 NH3 (g)

What is the value of K if at equilibrium a 3.0 L flask contains 0.45 mol of hydrogen, 0.75 mol of nitrogen,

and 0.30 mol of ammonia? (12)

  1. Given the reaction:N2(g) + O2(g)  2 NO (g)

An analysis of the equilibrium mixture in a 5.0 L flask gives the following results; 2.5 mol of oxygen, 3.5 mols of nitrogen, and 0.5 mol of nitrogen monoxide. What is the value of Kc? (0.029)

  1. In a closed container, nitrogen and hydrogen react to produce ammonia. At equilibrium the [N2] = 2.0 x 10 -4 M, [H2] = 4.0 x 10 -3 M, [NH3] = 2.2 x 10 -4 M. What is the Kc for the reaction? (3800)

N2(g) + H2(g)  NH3(g)

  1. For the given reaction of methanol, the equilibrium concentrations were found to be [CO] = 0.170 M, [H2] = 0.322, [CH3OH] = 0.0406. Find the value of Kc. (0.431)

CH3OH (g)  CO (g) + 2 H2(g)

  1. Bromine chloride, BrCl, decomposes to form bromine and chlorine.

2 BrCl (g) ↔ Cl2 (g) + Br2 (g)

At a certain temperature the equilibrium constant for the reaction is 11.1, and theequilibrium mixture contains 4.00 mol of Cl2. How many moles of Br2 and BrClare present in the equilibrium mixture? (1.20)

  1. The decomposition of hydrogen iodide to hydrogen and iodine occurs by thereaction

2 HI (g) ↔ H2 (g) + I2 (g)

Hydrogen iodide is placed in a container at 450°C an equilibrium mixturecontains 0.50 moles of hydrogen iodide. The equilibrium constant is 0.020 for thereaction. How many moles of iodine and hydrogen are present in theequilibrium mixture? (0.071)

EQUILIBRIUM EXPRESSIONS AND THE CONSTANT (TYPE III)______

C12-4-04:Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.

1.For the gas reaction A + B  AB , initially 1.0 mol of A and 1.0 mol of B were placed in a 1.0 L container. At equilibrium, the concentration of AB was 0.40 M.

a) Determine the value of the equilibrium constant.

b) What is the AB concentration if [A] = 1.2 M and [B] = 0.27 M?

c) What is [A] if [B] = 1.7 M and [AB] = 2.0 M? (1.1, 0.36, 1.1)

2.Consider the reaction:

CO2(g) + H2(g)  CO (g) + H20 (g)

Initially, 0.25 mol of water vapour and 0.20 mol of carbon monoxide are placed in a 1.00 L reaction vessel. At equilibrium, evidence shows that 0.10 mol of carbon dioxide is present. Calculate the Kc for the reaction. (1.5)

3.Consider the reaction:2 AB(g) A2(g) + B2(g)

4.0 mol of AB were placed in a 2.0 L flask and were allowed to reach equilibrium. At equilibrium, it was observed that 1.0 mol of A2 was present. What is the value of Kc? (0.25)

4.Initially, 0.10 mol of NO and 0.050 mol of H2, and 0.10 mol of H20 are placed in a 1.0 L container and allowed to react. At equilibrium the [NO] = 0.062 M. Calculate the equilibrium constant, K.

(Kc = 650)

2NO (g) + 2 H2(g)  N2(g) + 2 H20 (g)

5.In a 1 L heated reaction vessel the following concentrations were added, [SO2] = 2.0 M, [NO2] = 2.0 M. At equilibrium, [NO] = 1.3 M. Find the Kc. (3.5)

SO2(g) + NO2(g)  SO3(g) + NO (g)

6.Given the following reaction:

2 NH3(g)  N2(g) + 3 H2(g)

4.0 mol of NH3 were added to a 2.0 L flask. At equilibrium there were 2.0 mol present. Find the equilibrium concentrations for the other entities and solve for the equilibrium constant. (1.7)

7.Given the reaction:H2(g) + I2(g)  2 HI (g)

One mole of hydrogen and one mole of iodine are placed in a one litre container and allowed to react. What is the value of K at equilibrium if 1.36 mols of HI are present? (18.06)

8.For the gas reaction: A + B  2 C , 0.50 mol of each A and B are placed in a 1 L container and allowed to reach equilibrium. Equilibrium concentration of C = 0.0235 M. Determine the value of Kc . (0.002)

9.Initially, enough ammonia was dissolved in water to make a 0.0124 M solution. This was left at 25ºC to reach equilibrium, at which time it was found that the [OH -] = 4.64 x 10 -4 M. Calculate the remaining concentrations at equilibrium and find the value of Kc.

(0.0119, 4.64 x 10 -4, 1.81 x 10 -5)

NH3(g) + H2O(l)  NH4+(g) + 0H-(g)

10.Initially, 12.0 mol of SO3 was added to a 3.0 L reaction vessel. At equilibrium there were 3.0 mol of SO2 present. Find the value of Kc and the remaining equilibrium concentrations. (0.056)

2 SO3(g)  2 SO2(g) + O2(g)

11. Initially the concentrations of N2 and O2 are 1.8 mol/L each and there is no NO. If at equilibrium the [NO] is 2.0 mol/L, find K. (6.25)

N2(g) + O2(g)2 NO(g)

12.Find K for the reaction

2 CO(g) + O2(g)2 CO2(g)

If initially, there is 5.0 moles of CO, 10.0 moles of O2 and 1.0 mole of CO2 in a 2.0 L container and at equilibrium CO2 has a concentration of 2.5 mol/L.(6.25)

EQUILIBRIUM EXPRESSIONS AND REACTION QUOTIENT______

C12-4-03:Use the value of the reaction quotient, Qto explain how far a system at equilibrium has gone towards completion.

-Remember, calculate Q just like you would Kc:

  1. A vial contains 0.150 M of NO2 and 0.3 M N2O4. Calculate the Q of the reaction. (13.3)

2 NO2 (g)  N2O4 (g)

  1. For the reaction:A (s) + 2 B (g)  2 C (g)Kc = 25.0

[A] = 12.0 mol/L [B] = 2.0 mol/L [C] = 30.0 mol/L

a) Is the system at equilibrium.

b) Which reaction needs to be faster (favoured), forward or reverse?

c) Which concentrations are increasing or decreasing?

  1. At 448 ºC, Kc = 50.5 for the reaction,H2 (g) + I2 (g)  2 HI (g)

Find the Q and predict how the reaction proceeds if the concentration of hydrogen is 0.15 M, 0.175 M for Iodine, and 0.950 for hydrogen iodide. (34.4, right)

  1. At a given temperature, the K = 0.055 for the reaction that follows: (0.55, left)

PCl5(g) +  PCl3(g) + Cl2 (g)

Find Q and predict how the reaction proceeds if [PCl5] = 0.8 M, [PCl3] = 0.2 M, and [Cl2] = 2.20 M.

  1. At 753 ºC, Kc = 0.0060 for the decomposition of calcium carbonate, which is described by the following equation:

CaCO3 (s)  CaO (s) + CO2 (g)

Find Q and predict how the reaction will proceed if [CO2] = 0.0004 M. (0.0004)

  1. For the reaction:CO (g) + H2O (g)  CO2 (g) + H2 (g)

If Kc = 5.10 at 527ºC, and [CO] = 0.15 M, [H2O] = 0.25 M, [H2] = 0.42 M and [CO2] = 0.37 M, calculate Q and determine how the reaction will proceed. (4.1)

  1. Given the following equation:2 HI (g)  H2 (g) + I2 (g) Kc = 0.020

Is the system at equilibrium in each of the following cases? If not, predict the direction in which the reaction will proceed to reach equilibrium. (0.02, 0.34)

a) [HI] = 0.14 M, [H2] = 0.04 M, [I2] = 0.01 M

b) [HI] = 0.20 M, [H2] = 0.15 M, [I2] = 0.09 M

  1. Given the equilibrium system:PCl5(g) +  PCl3(g) + Cl2 (g)Kc = 12.5 at 60ºC

The contents of a 1.0 L reaction vessel is analyzed and found to contain 3.2 mol of Cl2, 1.5 mol of PCl3, and 2.0 mol of PCl5. Show that the reaction mixture has not yet reached equilibrium. (2.4)

  1. There exists an equilibrium if 5.0 moles of CO2, 5.0 moles of CO and 0.20 moles of O2

are in a 2.0 L container at 562°C. Find Kc for the reaction

2 CO (g) + O2 (g)  2 CO2 (g)

Would the system be at equilibrium if [CO2] = 15.8 mol/L, [CO] = 10.0 mol/L and

[O2] = 0.25 mol/L? If not, which reaction is favoured?

  1. For the reaction:4 NH3 (g) + 7 O2 (g)  4 NO2 (g) + 6 H2O (g)

Equilibrium is reached when [H2O] = 0.100 mol/L, [O2] = 2.00 mol/L, [NO2] = 0.200 mol/L and [NH3] = 0.500 mol/L.

If 0.75 moles of H2O, 12.0 moles of NO2, 30.0 moles of O2 and 0.30 moles of NH3 are in a 3.0 L container at the same temperature, is equilibrium achieved? If not, which reaction is favoured?

-Complete as a Type III question first to get concentrations, then determine Qc and compare to given Kc:

  1. For the reaction:2 SO2 (g) + O2 (g)  2 SO3 (g) Kc = 16.0

Initially, [SO2] = 5.0 mol/L, [O2] = 10.0 mol/L and [SO3] = 0.

After two hours [O2] = 7.9 mol/L. Is the system at equilibrium? If not, which substances

are increasing and which are decreasing?

  1. Keq = 46.0 for the reactionH2 (g) + I2 (g)  2 HI (g)

Initially there are 6.90 moles of H2 and 2.40 moles of I2 in a 1.00 L container. After 5

hours there is still 1.00 moles of I2 left. Is the system at equilibrium? If not, which

substances are increasing and which are decreasing?

SOLUBILITY EQUILIBRIA______

C12-4-11:Write solubility product (Ksp) expressions from balanced chemical equations for salts with low solubility and solve related problems.

1.Write the dissociation equation and the solubility product expression for each of the

following (assume that all the solid that dissolves exists as ions).

a. PbSO4d. SrCO3

b. Al2(SO4)3e. Ag2CO3

c. Ba(OH)2f. Fe2(SO4)3

2. From the following solubilities, calculate the Ksp. ** (watch units)

a. Ca3(PO4)2 7.15 x 10-7 M c. AgI 2.88 x 10–6 g/L

b. Pb(OH)2 4.20 x 10–6 mol/L d. CaF2 1.70 x 10-5 g/mL

3. A saturated solution of calcium hydroxide has an hydroxide ion concentration of

3.0 x 10-3 mol/L. Calculate the Ksp of calcium hydroxide.

4. At 25°C, a saturated solution of iron (III) hydroxide has an iron ion concentration

of 1.3 x 10-13 mol/L. Calculate the Ksp of iron (III) hydroxide.

5. If 6.7 x 10-5 g of AgBr is all that can be dissolved at 25°C in 500.0 mL, calculate

the solubility product of AgBr.

6. If [D+] is 2.00 x 10 -5 M at equilibrium, what is the Ksp for D2A?

7. Given the following compounds’ Ksp, calculate their solubilities in mol/L and g/L.

a. CuS Ksp = 6.31 x 10–36c. SrC2O4Ksp = 1.58 x 10–7

b. PbI2Ksp = 1.39 x 10–8d. Al(OH)3Ksp = 1.26 x 10–33

8. What are the equilibrium concentrations of all the ions in a saturated solution of

AgSCN at 25°C, if the Ksp is 1.6 x 10-14?

9. What are the equilibrium concentrations of all the ions in a saturated solution of

Cu(OH)2 at 25°C, if the Ksp is 1.6 x 10-19.

10.How many grams of each compound should be added to a 1.0 L container to have a saturated aqueous solution?

  1. Lead (II) sulfate, PbSO4Ksp = 1.3 x 10 -8
  2. Silver carbonate, Ag2CO3Ksp = 6.2 x 10 -12
  3. Magnesium hydroxide, Mg(OH)2Ksp = 1.2 x 10 -11

ANSWERS

2a) 2.02 x 10-29 b) 2.96 x 10-16c) 1.50 x 10-16 d) 4.12 x 10-11

3) 1.35 x 10-8 4) 7.7 x 10-51 5) 5.1 x 10-13 6) 4.0 x 10-15

7 a) 2.51 x 10-18M, 2.40 x 10-16 g/L b) 1.5 x 10-3M, 0.698 g/L

c) 3.97 x 10-4M, 6.97 x 10-2 g/L d) 2.61 x 10-9M, 2.04 x 10-7 g/L

8) 1.3 x 10-7M 9) 3.4 x 10-7M, 6.8 x 10-7 M 10) 0.0345g, 0.0317g, 0.00835g

LeCHATELIER’S PRINCIPLE AND STRESS______

C12-4-06:Use Le Chatelier’s principle to predict and explain shifts in equilibrium.

  1. For the reaction:PCl3(g) + Cl2(g) PCl5(g)H = -92.5 kJ

Predict the effect on the position of the equilibrium that results from

a) increasing the total pressure by decreasing volume.

b) injecting more Cl2 gas.

c) increasing the temperature.

d) increasing the volume of the container.

e) adding a catalyst.

  1. For the reaction:CH4(g) + H2O(g) + 49.3 kJ  CO(g) + 3 H2(g)

Predict the effect on the position of the equilibrium that results from

a) increasing temperature.

b) decreasing temperature.

c) decreasing the pressure.

d) decreasing the volume of the container.

e) adding a solid drying agent such as CaCl2 which reacts with H2O(g).

  1. For the reaction:9.4 kJ + 2 HI(g) H2(g) + I2(g)

a) What is the effect on [HI] if a small amount of H2 is added?

b) What is the effect on [HI] if the pressure of the system is increased?

c) What is the effect on [HI] if the temperature is increased?

d) What is the effect on [HI] if a catalyst is added?

  1. For the reaction:CO(g) + 2 H2(g) CH3OH(g) + energy

Predict the effect of the following changes on the equilibrium concentration of CH3OH(g)

a) a decrease in temperature.

b) an increase in pressure.

c) addition of H2(g).

d) addition of a catalyst.

  1. In the equilibrium reaction:2 NO(g) + O2(g) 2 NO2(g) + 114.6 kJ

What will be the change in the equilibrium [NO2] under each of the following conditions?

a) O2 is added.

b) NO is removed.

c) energy is added.

  1. For the following reaction:N2O4(g) + 58.9 kJ  2 NO2(g)

How will the equilibrium [NO2] be affected by the following?

a) an increase in pressure.

b) an increase in temperature.

c) the addition of a catalyst.

  1. Suggest 4 ways to increase the [SO3] in the following equilibrium reaction:

2 SO2(g) + O2(g) 2 SO3(g) + 192.3 kJ

  1. For the reaction:4 HCl(g) + O2(g) 2 H2O(g) + 2 Cl2(g) + 114.4 kJ

EXPLAIN how each of the following effect the position of the equilibrium.

a) the size of the container is increased.

b) energy added.

c) O2(g) added.

d) HCl(g) removed.

e) Adding a catalyst

  1. Nitric oxide gas, NO, releases 57.3 kJ/mol when it reacts with oxygen gas to give

nitrogen dioxide gas.

a) Write the equation for this reaction.

b) Predict the effect that increasing the temperature will have on

i) the equilibrium concentrations.

ii) the speed of formation of NO2.

LeCHATELIER’S PRINCIPLE AND STRESS______

C12-4-06:Use Le Chatelier’s principle to predict and explain shifts in equilibrium.

Include: Interpret concentration versus time graphs.

The above graph shows concentration versus time for a system containing carbon

monoxide (CO) dichlorine (Cl2) and phosgene (COCl2).

  1. Write a balanced equation to represent the reaction studied.
  1. How much time was required for the system to reach equilibrium?
  1. Calculate an approximate value for the equilibrium constant Kc using the concentrations at time t = 60 s.
  1. Explain the changes 70 s after the initiation of the reaction.
  1. What changes in conditions might have been imposed on the system 120 s after the initiation of the reaction?
  1. Are any events taking place between the interval 50 s and 70 s? between 280 s and 300 s? Explain your answers.
  1. What changes may have taken place at t = 320 s?
  1. What differences would you have noticed if a catalyst had been present during the entire course of this reaction?
  1. List the changes you might impose on this system if you wanted to produce a maximum amount of phosgene (COCl2)?
  1. Calculate the equilibrium constant for t = 100s, 300s and 500s. How could you account for the differences in the value calculated for the equilibrium constant Kc from the concentrations at different time points on the graph?

EQUILIBRIUM UNIT REVIEW______

  1. If 1.0 mol each of carbon dioxide and hydrogen is initially injected into a 10.0 L reaction chamber at 986ºC, what would be the concentrations of each entity at equilibrium?

(Kc = 1.60) (0.044, 0.044, 0.056, 0.056)

CO2(g) + H2(g)  CO (g) + H20 (g)

  1. Consider the reaction: 2 HBr (g)  H2(g) + Br2(g)

Initially, 0.25 mol of hydrogen and 0.25 mol of bromine are placed in 500 mL reaction vessel and heated. The Kc for the reaction is 0.020. Calculate the concentrations at equilibrium. (0.78, 0.11, 0.11)

  1. With reference to the equation:2 SO2(g) + O2 (g)  2 SO3 (g) (endothermic)
  1. What stresses will produce an increase in the quantity of SO3 produced, if the temperature is kept constant?
  2. What is the effect of a rise of temperature on the equilibrium?
  1. Hydrogen peroxide can be decomposed as follows:

H2O2(l)  H2 (g) + O2 (g) (exothermic)

Equilibrium is established in a 10 L flask at room temperature. Predict the direction of the equilibrium shift.

  1. hydrogen gas is added to the flask.
  2. The temperature is raised to 500 ºC.
  3. The entire mixture is compressed into a smaller volume.
  1. For the given reaction of methanol, the equilibrium concentrations were found to be [CO] = 0.170 M, [H2] = 0.322, [CH3OH] = 0.0406. Find the value of Kc. (0.434)

CH3OH (g)  CO (g) + 2 H2(g)

  1. Write the equilibrium constant expression for the following chemical reaction:

H2 (g) + Cl2 (g)  2 HCl (g)

  1. At 448 ºC, Kc = 50.5 for the reaction,H2 (g) + I2 (g)  2 HI (g)

Find the Q and predict how the reaction proceeds if the concentration of hydrogen is 0.15 M, 0.175 M for Iodine, and 0.950 for hydrogen iodide. (34.4)

  1. Define, in detail, the following terms: closed system, equilibrium, dynamic equilibrium,

Le Chatelier’s principle.

  1. For the all-gas reaction of N2 + O2  2 NO, the equilibrium constant is 1.0 x 10 -30 at room temperature, and then 0.1 at 2000ºC. Which reaction, the forward or reverse,
  2. Is favor at room temperature?
  3. Is favored at the higher temperature?
  4. is the forward reaction endothermic or exothermic? Explain.
  1. One liter of water is able to dissolve 2.5 x 10 -3 mol of PbF2. What is the Ksp for this compound?

(6.2 x 10-8)

  1. The Ksp of PbI2 is 8.3 x 10 -9. What is the molar solubility of this compound in water?

(1.28 x 10-3 mol/L)

  1. Arrange the following ionic solids in order of decreasing solubility at room temperature, on the basis of their Ksp values:
  2. BaCO3 = 2 x 10 -9
  3. CaCO3 = 5 x 10 -9
  4. MgCO3 = 2 x 10 -8
  5. PbCO3 = 7.4 x 10 -14
  1. A saturated aqueous solution of barium sulfate, BaSO4, a slightly soluble ionic compound has added to it a few crystals of sodium sulfate, which is readily soluble in water.
  2. In terms of a shift in the position of equilibrium, describe what happens when the sodium sulfate is added to the solution.
  3. How will this shift affect the concentration of barium and sulfate ions?
  4. How will this shift affect the mass of BaSO4?