1) Cyanic acid, HOCN(aq), is a weak acid

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1) Cyanic acid, HOCN_(aq), is a weak acid. A 0.100 mol/L solution of cyanic acid is found to be 4.7% ionized. Calculate the K_a for cyanic acid. (Hint: ionization below 5% can be considered insignificant when finding the equilibrium concentration for HOCN)

                                   HOCN _(aq)     ↔  H¹⁺ _(aq)  +  OCN^1- _(aq)

2) IIf the pH of an acid solution at 25^oC is 6.18, what is the:

a) pOH

b) [H¹⁺] in mol/L

c) [OH^1-] in mol/L

 

3) Clearly identify the two conjugate acid - base pairs in the following equilibrium equation of Arsenic acid, H₃AsO₄ (aq) reacting with water.

H₃AsO₄ (aq) + H₂O (l) ↔ H₂AsO₄ ^1- (aq) + H₃O ¹⁺ (aq)

 

4) 1.2 mol of CH₃OH_(g) are injected into a 2.0 L container and the following equilibrium becomes established.

2H_2(g) + CO_(g) « CH₃OH_(g) + 92 kJ

 

Calculate the equilibrium constant (K) if at equilibrium 1.0 mol of CH₃OH_(g) is still in the container.

 

5) The equilibrium system shown below has a K = 8.3 X 10^-2.

2A_(g) + B_(s) « C_(s) + 3D_(g)

a) Write the equilibrium law expression for the reverse reaction.

    b) Calculate the value of K of the reverse reaction.

 

6) The Ksp's of CuCl and TlCl are 1.9X10^-7 and 1.8 X 10^-4 respectively. Which is more soluble?

 

7) The following equation represents one method for making Ammonia

N_2(g) + 3H_2(g) <--> 2NH_3(g) + 92kJ

Predict the effect on the equilibrium concentrations of all substances if:

a) the temperature is increased.

b) the pressure is increased.

 

8) The equilibrium system shown below was analyzed and the concentrations of HI(g), H2(g), and I2(g) were found to be 4.4 mol/L, 3.2 mol/L, 1.5 mol/L respectively. The equilibrium constant must be which of the following?

H2(g) + I2(g) <--> 2HI(g) + 65 kJ

a) 4.0

b) 0.25

c) 0.92

d) 1.1

e) 0.16

 

9) What is the maximum concentration of Ca²⁺ ions in a solution containing 0.010 M of F^- ions?

a) 8.5 x 10^-9 M

b) 1.7 x 10^-8 M

c) 3.9 x 10^-7 M

d) 1.7 x 10^-6 M

 

10) For the equilibrium system below, which of the following would result in an increase in the quantity of PCl5(g)?

PCl3(g) + Cl2(g) <--> PCl5(g) + 45 kJ

a) increasing temperature

b) increasing the size of the container

c) decreasing temperature

d) removing some Cl_2(g)

e) injecting some He gas