Heating solid sodium bicarbonate in a closed vessel...

Heating solid sodium bicarbonate in a closed vessel establishes the following equilibrium: $$ 2 \mathrm{NaHCO}_{3}(s) \rightleftharpoons \mathrm{Na}_{2} \mathrm{CO}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(g)+\mathrm{CO}_{2}(g) $$ What would happen to the equilibrium position if (a) some of the $\mathrm{CO}_{2}$ were removed from the system; (b) some solid $\mathrm{Na}_{2} \mathrm{CO}_{3}$ were added to the system; (c) some of the solid $\mathrm{NaHCO}_{3}$ were removed from the system? The temperature remains constant.

Heating solid sodium bicarbonate in a closed vessel establishes the following equilibrium:
$$
2 \mathrm{NaHCO}_{3}(s) \rightleftharpoons \mathrm{Na}_{2} \mathrm{CO}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(g)+\mathrm{CO}_{2}(g)
$$
What would happen to the equilibrium position if
(a) some of the $\mathrm{CO}_{2}$ were removed from the system; (b) some solid $\mathrm{Na}_{2} \mathrm{CO}_{3}$ were added to the system; (c) some of the solid $\mathrm{NaHCO}_{3}$ were removed from the system? The temperature remains constant.

Key Concepts

Effect of Concentration/Partial Pressure Changes on Equilibrium

Variations in the concentration or partial pressure of reacting species, especially those in the gas phase, directly impact the reaction quotient and shift the equilibrium position according to Le Chatelier's Principle. Removing a gaseous product, for instance, reduces its partial pressure, leading the equilibrium to shift in a direction that replenishes the gas, whereas changes in the amount of a solid leave the equilibrium largely unaffected due to their constant activity.

Heterogeneous Equilibria and the Role of Phases

In heterogeneous equilibria, the reactants and products exist in different phases (e.g., solids, liquids, gases), and the activities of pure solids and liquids are typically constant and do not appear in the equilibrium expression. This means that changes in the amount of a pure solid do not affect the equilibrium position in the same way that changes in the concentration or partial pressure of a gas or solute would.

Chemical Equilibrium

Chemical equilibrium is the state in which the forward and reverse reactions occur at the same rate, leading to constant concentrations of reactants and products over time. This concept provides the framework for understanding how systems adjust when disturbed, as the reaction tends to reach a new balance in response to external changes, while the equilibrium constant remains unaltered at a given temperature.

Le Chatelier's Principle

Le Chatelier's Principle is a guideline stating that if an external change is applied to a system at equilibrium, such as a change in concentration, pressure, or temperature, the system will adjust its position to counteract the imposed change and restore a new equilibrium. This principle is key in predicting the qualitative shift in reaction favorability when the conditions of a reaction are altered.

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