Analytical Chemistry: Equilibrium Concept

For the equilibrium reaction 2SO₂ (g) + O₂ (g) ⇌ 2SO₃ (g), ΔHº_rxn= –198 kJ/mol. Which one of these factors would cause the equilibrium constant to increase?

• Decrease the temperature.

• Remove O gas.

• Add SO gas.

• None of these.

• Add a catalyst.

The Kc for the reaction CO2 (g) + H2 (g) ⇌ H2O(g) + CO(g) is 1.6 at about 990ºC. Calculate the number of moles of hydrogen gas in the final equilibrium system obtained by initially adding 1.00 mol of H2, 2.00 mol of CO2, 0.750 mol of H2O, and 1.00 mol of CO to a 5.00 L reactor at 990ºC.

• 0.62 mol

• 1.02 mol

• 0.42 mol

• none of the above

• 0.82 mo

Calculate K for the reaction 2HI(g) ⇌ H2 (g) + I2 (g) given that the concentrations of each species at equilibrium are as follows: [HI] = 0.85 mol/L, [I2] = 0.60 mol/L, [H2] = 0.27 mol/L.

• 4.5

• 5.25

• 1.6 × 10²

• 0.22

• 0.19

For the following reaction at equilibrium, which gives a change that will shift the position of equilibrium to favor the formation of more products? 2NOBr(g) ⇌ 2NO(g) + Br2(g), ΔHºrxn= 30 kJ/mol

• Remove Br2

• Remove NOBr selectively

• Lower the temperature.

• Increase the total pressure by decreasing the volume.

• Add more NO.

Consider the gas-phase equilibrium system represented by the equation: 2H2O(g) ⇌ 2H2 (g) + O2 (g)

Given that the forward reaction is endothermic, which of the following changes will decrease the equilibrium amount of H2O?

• adding more oxygen

• decreasing the volume of the container

• adding He gas

• increasing the temperature at constant pressure

• adding a solid phase calalyst

In which of these gas-phase equilibria is the yield of products increased by increasing the total pressure on the reaction mixture?

• H2 (g) + I2 (g) ⇌ 2HI(g)

• PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)

• 2SO3 (g) ⇌ 2SO2 (g) + O2 (g)

• CO(g) + H2O(g) ⇌ CO2(g) + H2(g)

• 2NO(g) + Cl2(g) ⇌ 2NOCl(g)

The equilibrium between carbon dioxide gas and carbonic acid is very important in biology and environmental science.

CO2(aq) + H2O (l) ⇌ H2CO3 (aq)

Which one of the following is the correct equilibrium constant expression (Kc) for this reaction?

Type as: Kc = [X2Y3][AB2]/[ZC][X2B]

Consider this reaction at equilibrium: 2SO (g) + O (g) ⇌ 2SO (g), ΔHº = –198 kJ/mol If the volume of the system is compressed at a constant temperature, what change will occur in the position of the equilibrium?

• A shift to produce more SO2

• No change

• A shift to produce more O2

• A shift to produce more SO3

For the reaction SO2 (g) + NO2 (g) ⇌ SO3 (g) + NO(g), the equilibrium constant is 18.0 at 1,200ºC. If 1.0 mole of SO2 and 2.0 moles of NO2 are placed in a 20. L container, what concentration of SO3 will be present at equilibrium?

• 0.48 mol/L

• 18 mol/L

• 2.22 mol/L

• 0.95 mol/L

• 0.11 mol/L

For the reaction HCN (aq) + H2O (l) ⇌ CN- (aq) + H3O+ (aq), all of the following will shift the equilibrium toward the products, except:

I. adding HCN II. adding H2O

III. removing CN- IV.removing H3O+

• II

• I, III, IV

• II, IV

• III

• I