Revise smart, understand Better

5/27 MCQs for:

MATTER: PROPERTIES AND TRANSFORMATION: Reversible Reactions

A reversible reaction is represented by the sign:

⇌ between reactants and products and ⇄ between reactants and products.

⇌ between reactants and products.

⇾ between reactants and products.

⇄ between reactants and products.

A reversible reaction is said to have attained equilibrium when:

The rate of the forward reaction is equal to the rate of the backward reaction and the concentrations of reactants and products remain constant.

The rate of the forward reaction is not equal to the rate of the backward reaction and the concentrations of reactants and products remain constant.

The rate of the forward reaction is equal to the rate of the backward reaction and the concentrations of reactants and products are the same.

The rate of the forward reaction is equal to the rate of the backward reaction.

Sulphur dioxide and oxygen combine reversibly to produce sulphur trioxide in presence of vanadium (V) oxide as a catalyst.

2SO_{2 (g)} + O_{2 (g)} ⇌ 2SO_{3 (g)} ∆H = -197 KJ/mol

Choose the correct statement(s) below concerning the above process:

The use of excess amounts of reactants will shift the equilibrium position to the right favouring the production of SO₃. If SO₃ is removed continually by dissolving in concentrated sulphuric acid to form oleum, the equilibrium position will shift to the right favouring the production of SO₃.

Since the forward reaction is exothermic, a low temperature will shift the equilibrium position to the right, favouring the production of SO₃, according to Le Chatelier’s principle. The optimum temperature for the reaction is between 450℃-500℃. Lower temperatures than 450 ℃ will give higher yields of SO₃ but will render the process uneconomical because the reaction will be too slow.

All are correct.

An increase in pressure will shift the equilibrium position to the right, hence increasing the yield of SO₃. In practice atmospheric pressure of 1atm is sufficient to give high yields of SO₃.

Consider the following reaction system in equilibrium:
2SO_{2 (g)} + O_{2 (g)} ⇌ 2SO_{3 (g)} ∆H=-197KJmol⁻¹
According to Le Chatelier’s principle, if the temperature is increased.

The equilibrium position will shift to the left favouring the endothermic reaction so that the extra heat added is used up.

The equilibrium position will shift to the right i.e. the exothermic reaction will be favoured so as to replenish the heat removed from the system.

The equilibrium position will shift to the left i.e. the exothermic reaction will be favoured so as to replenish the heat removed from the system.

The equilibrium position will shift to the right and then to the left i.e. the exothermic reaction will be favoured so as to replenish the heat removed from the system.

Consider the following systems in equilibrium:

N_{2 (g)} (1 mole) + 3H_{2 (g)}(3 moles) ⇌ 2NH_{3 (g)} (2 moles) ---------------------- (1)

For system (1):

4 moles of gas molecules on the LHS and 2 moles on the RHS.

If pressure is reduced, the equilibrium will shift to the left to produce more gas molecules thereby increasing the pressure of the system in accordance with Le Chatelier’s principle.

If pressure is increased, the equilibrium position will shift to the right to produce fewer gas molecules thereby reducing the pressure of the system according to Le Chatelier’s principle.

All are correct.