Equilibrium Practice Problems Name ______

Equilibrium Practice Problems Name ______

Write your work and answers on a sheet of lined paper. This will be collected

1. Write the equilibrium expression for each of the following reactions:

a.  2 BrF5 (g)↔ Br2 (g) + 5 F2 (g)

b.  4 NH3 (g) + 3 O2 (g) ↔2 N2 (g) + 6 H2O (g)

c.  2 NH3 (g)↔ N2 (g) + 3 H2 (g)

d.  3 O2 (g) ↔2 O3 (g)

e.  C (s) + O2 (g) ↔CO2 (g)

f.  NH4HS (s)↔ NH3 (g) + H2S (g)

2. Determine the equilibrium constant for the following reaction if the concentration of [N2O4] = 1.50 X 10-3 and [NO2] = 0.571 in the reaction N2O4 (g) ↔ 2 NO2 (g)

Answer Keq = 217

3. Calculate the Keq for the reaction C (s) + O2 (g) ↔CO2 (g) if the equilibrium concentration of [O2] = 0.0025 and the [CO2] = 0.0033

Answer Keq = 1.3

4. For the reaction, 2SO2 (g) + O2 ↔ 2SO3 (g) , the equilibrium concentrations of the sulfur oxides are [SO2] = 2.00 and the [SO3] = 10.0 What is the equilibrium concentration of oxygen when the Keq is 800.0 for the reaction?

Answer [O2] =0.0312 M

5. Determine the equilibrium concentration when 1.00 mole of I2 and 1.00 mole of H2 are initially placed in a 5.0 Liter container and produce HI. At the reaction temperature the Keq is 6.4 x 10-6 (HINT – use an icebox. Drop x in (0.20 –x) since x is so small compared to the other values in the problem)

Answer x= 2.5 x10 -4 , H2= .20 – x = .20, I2 = .20 – x = .20, HI = 2X = 5.0 x 10-4M

6. At a specific temperature, 0.750 mole of each reactant (CO2 (g) and H2O(g)) is added to a 1.0 Liter container. At equilibrium, the [CO2 (g)] is 0.0210. What is the value of Keq for the reaction?

(Product is H2CO3 (aq)) Answer – Keq = 1650

7. The Keq is 4.20 x 10 -6 for the equilibrium reaction PCl5 (g) ↔ PCl3 (g) + Cl2 (g) . Determine the equilibrium concentration of all the species if the initial concentration of the PCl5 is 0.0500M(HINT – use an icebox. Drop x in (0.0 500–x) since x is so small compared to the other values in the problem)

Answer [PCl5] = .0495 M [PCl3] = 4.58 X 10 -4 M [Cl2] = 4.58 x 10 -4M

8. Consider the reaction 2 NOBr (g) ↔2 NO (g) + Br2 (g) DH°= +30 kJ

Which of the following changes will cause the equilibrium to shift to the right? (choose more than one)

A. increasing temperature D. adding NOBr

B. increasing pressure E. adding NO

C. increasing volume F. removing Br2

9. Which of the following reactions will have a larger equilibrium constant at 1000 K than at 298 K?

A. 2 NOBr (g) ↔2 NO (g) + Br2 (g) DH° = +30 kJ

B. 2 SO2 (g) + O2 ↔(g) 2 SO3 (g) DH° = –198 kJ

C. 2 NO (g) ↔ N2 (g) + O2 (g) DH °= –180 kJ

10. Which of the following reactions will not experience a shift in equilibrium when pressure

increases?

A. 2 NOBr (g) ↔ 2 NO (g) + Br2 (g) C. 2 NO (g) ↔ N2 (g) + O2 (g)

B. 2 SO2 (g) + O2 ↔ (g) 2 SO3 (g) D. 3 O2 (g) ↔ 2 O3 (g)