For the following equations, tell in which direction, left or right, the equilibrium will shift when these changes are made: The temperature is increased, the pressure is increased by decreasing the volume of the reaction vessel, and a catalyst is added.

(a) $2 \mathrm{~SO}_3(g)+197 \mathrm{~kJ} \rightleftharpoons 2 \mathrm{~SO}_2(g)+\mathrm{O}_2(g)$
(b) $4 \mathrm{~NH}_3(g)+3 \mathrm{~O}_2(g) \rightleftharpoons 2 \mathrm{~N}_2(g)+6 \mathrm{~H}_2 \mathrm{O}(g)+1531 \mathrm{~kJ}$
(c) $\mathrm{OF}_2(g)+\mathrm{H}_2 \mathrm{O}(g) \rightleftharpoons \mathrm{O}_2(g)+2 \mathrm{~HF}(g)+318 \mathrm{~kJ}$

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In this task, we need to determine in which direction equilibrium will shift.

The $\textbf{equilibrium position}$ can be affected by changing the $\textbf{concentration, pressure and temperature}$ . If one of the conditions under which the system is in a state of chemical equilibrium changes, then the equilibrium shift will be in the direction of that reaction which tends to oppose that change and to establish the previous conditions. This legality is known as the $\textbf{Le Chatelier's principle}$ .

As the $\textbf{concentration}$ of $\textbf{reactants}$ $\textbf{increases}$ or the $\textbf{product}$ is $\textbf{removed }$ from the reaction mixture, equilibrium shifts in the direction of $\textbf{product formation}$ . An equilibrium shift in the $\textbf{direction of the reactants}$ in a reaction mixture is achieved by the opposite action, ie by $\textbf{reducing the concentration of reactants}$ or by $\textbf{increasing the concentration of the product}$ .

How the shift in equilibrium in a reaction system will be affected by a change in temperature depends on whether it is an exothermic or an endothermic reaction.

If the reaction is $\textbf{exothermic}$ , by $\textbf{cooling}$ the equilibrium of the reaction shifts $\textbf{towards the products}$ , while by $\textbf{heating}$ the exothermic reaction the equilibrium shifts $\textbf{towards the reactants}$ .

The opposite is true for $\textbf{endothermic}$ reactions. By $\textbf{heating}$ the equilibrium shifts $\textbf{towards the products}$ , and by $\textbf{cooling towards the reactants}$ .

Change in volume affect the reaction rate when one or more of the reactants or products is a gas. The volume affects on pressure. If the $\textbf{volume}$ of the container is $\textbf{decreased}$ , the $\textbf{pressure}$ of the gas will $\textbf{increase}$ . The change in pressure affects the equilibrium shift in the reaction mixture of gases.

As the total $\textbf{pressure}$ in the gaseous reaction mixture $\textbf{increases}$ , the equilibrium shifts in a direction that leads to a $\textbf{decrease}$ in the $\textbf{number of molecules}$ .

As the $\textbf{pressure decreases}$ , the equilibrium shifts in a direction that leads to an $\textbf{increase}$ in the $\textbf{number of molecules}$ .