Chemical Equilibrium Quiz

A chemical system is considered to have reached dynamic equilibrium when

• the frequency of collisions between the reactant molecules is equal to the frequency of collisions between the product molecules.

• the sum of the concentrations of each of the reactant species is equal to the sum of the concentrations of each of the product species.

• the activation energy of the forward reaction is equal to the activation energy of the reverse reaction.

• the rate of production of each of the products is equal to the rate of their consumption by the reverse reaction.

• the rate of production of each of the product species is equal to the rate of consumption of each of the reactant species.

In a study of the system, H2(g) + I2(g) --> 2 HI(g), at 699 K, several different reaction mixtures, described below, were prepared, placed in 5.00 liter containers, and allowed to attain equilibrium at 699 K. Despite having the different starting compositions shown, four of the five mixtures had the identical composition at equilibrium. Which one of the systems attained a different equilibrium composition than the others?

• System 1: 0.100 moles of H2, 0.000 moles of I2 and 0.600 moles of HI

• System 2: 0.175 moles of H2, 0.075 moles of I2 and 0.450 moles of HI

• System 3: 0.400 moles of H2, 0.300 moles of I2 and 0.000 moles of HI

• System 4: 0.150 moles of H2, 0.100 moles of I2 and 0.500 moles of HI

• System 5: 0.300 moles of H2, 0.200 moles of I2 and 0.200 moles of HI

Given the two reactions shown with their equilibrium constants,
PCl3(g) + Cl2(g) --> PCl5(g) K1
NO(g) + Cl2(g) --> 2 NOCl(g) K2
What is the equilibrium constant for the reaction, PCl5(g) + 2 NO(g) PCl3(g) + 2 NOCl(g)

• K1K2

• K2/K1

• K1/K2

• (K1K2)−1

• K2−K

The equilibrium constant for the reaction, H2(g) + I2(g) --> 2 HI(g) is 54.9 at 699.0 K. What is the equilibrium constant for 4 HI(g) 2 H2(g) + 2 I2(g) under the same conditions?

• 109.8

• 0.00911

• 0.000332

• −109.8

• 0.0182

For a specific reaction, which statement can be made about the equilibrium constant?

• It can change with temperature.

• It may be changed by addition of a catalyst.

• It increases if the concentration of one of the products is increased.

• It increases if the concentration of one of the products is decreased.

• It always remains the same.

For the chemical reaction, N2(g) + 3H2(g) --> 2NH3(g), Kc = 4.2 x 10^2 at some temperature which we call T1. 4.00 moles of NH3 were placed in a 50.0 liter container and it was brought up to T1 and allowed to come to equilibrium. Which situation below is true, at equilibrium?

• [NH3] = 3 × [H2]

• [NH3] > [H2]

• [H2] > [NH3]

• [NH3] = [H2]

• [N2] = [NH3]

For the reaction, 2SO2(g) + O2(g) --> 2SO3(g), at 900.0 K the equilibrium constant, Kc, has a value of 13.0. Calculate the value of Kp at the same temperature.

• 97.3 × 10^3

• 0.176

• 960

• 0.00174

• 0.077

A student is preparing a study of the reaction, 2CO2(g) --> 2CO(g) + O2(g), for which Kc = 26.2 at 827 °C. What is the value of Kp at that same temperature?

• 2.90 x 10^-1

• 3.86 x 10^-1

• 1.78 x 10^3

• 2.37 x 10^3

• 2.40 x 10^5

For which one of the following reactions is Kp equal to Kc?

• 4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g)

• C(s) + CO2(g) --> 2CO(g)

• 6CO2(g) + 6H2O(l) --> C6H12O6(s) + 6O2(g)

• CaCO3(s) --> CaO(s) + CO2(g)

• H2O(g) + C(s) --> H2(g) + CO(g)

The concentration of a pure solid or a pure liquid is left out of the expression for the equilibrium constant because

• solids and liquids drive the reaction in an undetermined fashion.

• solids and liquids do not react.

• their concentrations cannot be determined.

• solids and liquids react too slowly.

• their activity is constant and independent of