Suppose the flask is already at equilibrium but then the volume of the reaction flask is then reduced what will happen

1) Answer is: c) The reaction will proceed right.

Balanced chemical reaction: N₂(g) + 3H₂(g) ⇄ 2NH₃(g) ΔH = +92 kJ.

Reducing the volume of the system increase the partial pressures of the products and reactants.

With a pressure increase due to a decrease in volume, the side of the equilibrium with fewer moles is more favorable, there are 4 moles at the left side (three moles of hydrogen and one mole of nitrogen) and 2 moles (ammonia) at the right side of the reaction.

2) Answer is: d) The partial pressure of ammonia will increase.

This reaction is endothermic (enthalpy is higher than zero), which means that heat is added.

According to Le Chatelier's principle when the reaction is endothermic heat is included as a reactant and when the temperature increased, the heat of the system increase, so the system consume some of that heat by shifting the equilibrium to the right,  producing more ammonia.

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