15.1.2 The Law of Mass Action and Types of Equilibrium

Question 1

When sulfur dioxide is passed over calcium oxide, it combines with CaO to form CaSO3. This is one of the ways sulfur dioxide can be removed from a gas mixture. The reaction taking place is as follows: CaO(s) + SO2(g) CaSO3(s)

Which of the following expressions defines the equilibrium constant for this reaction?

Answer 1

Kc = 1 / [SO2 ]

Question 2

Consider the following reaction:

2NaHSO3(s) Na2SO3(s) + H2O(g) + SO2(g)

How will the position of equilibrium be affected by removing NaSO3 from the reaction vessel?

Answer 2

remains unaffected

Question 3

Is the following statement true or false?

In general, once equilibrium is achieved, the rates of the forward and the backward reactions are equal and so are the amount of reactants and products.

Answer 3

false

Question 4

NH4SH placed in a vessel at 22 degrees C, decomposes to form NH3 and H2S.

NH4SH NH3(g) + H2S(g)

Calculate the equilibrium concentration of NH3 and H2S if 4g of pure NH4SH is placed in a closed vessel, given that Kc=1.2 x 10^-4 at 22 degrees C.

Some of the solid remains when the system has come to equilibrium.

Answer 4

[NH3] = [H2S] = 1.1 x 10^-2

Question 5

After equilibrium is achieved in a homogenous gaseous reaction, it is changed by adding more reactants. This results in a new equilibrium. How is the equilibrium constant of the new equilibrium related to the old equilibrium constant value?

Answer 5

The new equilibrium constant value is the same as the old one.

Question 6

Gold ions react with copper metal to give gold metal and cupric ions.

2Au3+(aq) + 3Cu(s) 2Au(s) + 3Cu2+(aq)

What is the equilibrium expression for this reaction?

Answer 6

Keq = [Cu2+]3 / [Au3+]2

Question 7

What is the equilibrium expression for the following reaction?

Mn(OH)2(s) Mn2+(aq) + 2OH-(aq)

Answer 7

Ksp = [ Mn2+ ] [OH − ]2

Question 8

What is the equilibrium expression for the following equilibrium?

Al3+(aq) + H2O(l) H+(aq) + AlOH2+(aq)

Answer 8

Kc = [H+][AlOH2+] / [Al3+]

Question 9

What is the equilibrium expression for the following reaction in aqueous solution?

Ag+(aq) + 2NH3(aq) Ag(NH3)2+(aq)

Answer 9

Kc = [Ag(NH3)2+] / (Ag+

Question 10

Lead sulfate is a salt that is partially soluble in water. If the Ksp value for lead sulfate (PbSO4) is 1.3 x 10^-8, what are the concentrations of lead ions and sulfate ions in solution? Assume PbSO4 is the only solute in the solution.

Answer 10

[Pb2+] = [SO4^2-] = 1.1 x 10^4-