Question

I have a few chemical equilibrium and reaction questions I am stuck on.

1) Consider the following chemical equilibrium:

Heat + CO + 2H₂ ⇌ CH₃OH

Cooling the reaction mixture will...

a. decrease amounts of CO(g)

b. decrease amounts of CH3OH

c. increase amounts of CH3OH

d. decrease amounts of H2

2)

Consider the following chemical equilibrium:

H₂ + Cl₂ ⇌ 2HCl

Increasing the reaction mixture will...

a. have no effect

b. shift the reaction toward the reactant side

c. shift the reaction toward the product side

d. increase amount of the product

Answer 1

1)

Given equilibrium is

$Heat + CO + 2H_{2} \rightleftharpoons CH_{3}OH$

In the given equilibrium, forward reaction is endothermic and backward reaction is exothermic.

According to Lechatlier's principle, when a system is at equilibrium and the factors affecting the equilibrium such as concentration, temperature, pressure... are changed, the equilibrium shifts in a direction to reduce or nullify the the change (OR)

When a stress is applied on a system is at equilibrium, the system moves in a direction to reduce or nullify the stress.

Effect of Concentration : If concentration of reactants is increased, the equilibrium shifts in a direction to reduce the concentration of reactants ie rate of forward reaction increases. Similarly if concentration of products is increased, the equilibrium shifts in a direction to reduce the concentration of products ie rate of backward reaction increases.

Effect of temperature: If forward reaction is exothermic, the backward reaction becomes endothermic. Similarly if forward reaction is endothermic, backward reaction becomes exothermic.

Generally exothermic reactions are favourable at low temperatures and endothermic reactions are favourable at high temperatures.

On cooling, the reaction moves in a direction to increase the temperature. ie exothermic reaction takes place.

Hence backward reaction takes place.

Decreases the amounts of methanol (CH3OH).

Option B is the correct answer.

2)

The given equilibrium is

$H_{2}+ Cl_{2} \rightleftharpoons 2 HCl$

If the reaction mixture ie Hydrogen and Chlorine gas is increased, the equilibrium shifts in a direction to shift towards right side. ie equilibrium shifts towards products side.

Option C is the correct answer.

Option D is also correct as forward reaction increases, the concentration of products increases.