Reaction 1: 2NO(g) + Br2(g) ⇄ 2NOBr(g) ΔH°rxn = −16 kJ Kp = 27 at 25°CReaction 2: CO2(g) ⇄ C(s) + O2(g) ΔH°rxn = +100 kJ Kp = 2.6x10−9 at 25°C8. For which reaction(s) above would an increase in reaction vessel volume at constant temperature result in an increase in product yield? A) Reaction 1 only B) Reaction 2 onlyC) Both reactionsD) Neither reactionFor which reaction(s) above would an increase in temperature at constant volume result in an increase in product yield? A) Reaction 1 only B) Reaction 2 onlyC) Both reactionsD) Neither reaction

A reversible reaction intends to achieve the equilibrium, a state in the velocity of product formation is equal to the velocity of reactants formation. This equilibrium can be disturbed by some alterations in the reaction, and, by Le Chatelier's principle, the reaction will shift in to reestablish the equilibrium.

The equilibrium may be shift for three principal factors: concentration, temperature, and pressure. If a concentration of some of the substance increases, the reaction will shift to consume it; if it decreases, the reaction is shifted to form more this substance.

When the temperature of the system increases, the reaction shifts for the consume of the heat, thus, the endothermic reaction (ΔH°rxn > 0) is favored; if it decreases, the exothermic reaction (ΔH°rxn < 0) is favored. If the direct reaction is endothermic, the inverse is exothermic, and vice versa.

When the pressure of the system increases, the volume decreases, so, the equilibrium shifts for the less gas volume, or the side with fewer moles of gas substance; if the pressure decreases the inverse occurs.

So, if the vessel volume increases, the pressure will decrease, and so, the formation of more gas substances is favored. In reaction 1, in the reactants, there are 3 moles ( 2 of NO + 1 of Br2), and in the products 2 moles, so the reactants are favored, and the product yield decreases. In reaction 2, there is 1 mol on both sides of the reaction, so the pressure doesn't affect the equilibrium.

The increase in temperature favors the endothermic reaction. The reaction 2 has it's direct reaction endothermic, so the product yield increases. In reaction 1, the reactants increases, because the inverse reaction is endothermic.