Chapter 15 Multiple-choice questions

. Which one of the following statements regarding a dynamic equilibrium is false?

At equilibrium, there is no net change in the system

At equilibrium, the concentration of reactants and products stays the same

At equilibrium, the forward and back reactions cease to occur

At equilibrium, the rates of the forward and back reactions are identical

. At equilibrium, the concentrations of the reactants and products will be equal. True or false?

True

False

. Consider the reaction 2H₂ + O₂ ⇌ 2H₂O. Which one of the following correctly states the expression for the equilibrium constant for this reaction?

. A large value of K tells us which one of the following?

The reaction lies to the left

The reaction lies in the middle

The reaction lies to the right

. The value of the equilibrium constant, K, depends on the temperature at which the reaction is happening. True or false?

True

False

. Consider the binding of a protein and its ligand, represented by the expression P + L ⇌ PL. Which of the following statements in relation to this binding process is true?

The expression for the dissociation constant, K_d, is

A small value of K_d tells us that the protein and ligand bind tightly.

If binding is strong, the association reaction lies to the left.

If binding is weak, the dissociation reaction lies to the left.

. Consider the binding of oxygen to haemoglobin: Hb + O₂ ⇌ Hb-O. If we decrease the pressure of the system, what is the effect on this equilibrium reaction?

The equilibrium shifts to the left

The equilibrium shifts to the right

There is no change in the system

. Which one of the following statements regarding chemical equilibria is false?

Catalysts do not alter the position of equilibrium: they do not shift the equilibrium to the left or right

At equilibrium, ∆G = 0

If ∆G for a reaction is negative, the forward reaction happens spontaneously

If the equilibrium constant is very large, ∆G is positive

. Increasing the temperature of the surroundings shifts the position of equilibrium in favour of exothermic reactions. True or false?

True

False

. The free energy change under standard conditions (∆G°) is related to the equilibrium constant by the van't Hoff isotherm: ∆G° = -RTlnK. But what does the symbol R represent?

The entropy of the system

The gas constant

The Avogadro constant

The reaction quotient

. The combustion of carbon in oxygen under standard conditions:
C(s) + O₂(g) ⇌ CO₂(g) has a Gibbs free energy change of -394.4 kJ mol-1. In what direction does this equilibrium reaction shift if the temperature is lowered?

It shifts to the left: the back reaction is favoured

Nothing happens: the position of equilibrium is unchanged

It shifts to the right: the forward reaction is favoured

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