Final answer:
The yield of diiodine pentoxide (I2O5) in the given exothermic equilibrium can be increased by decreasing the temperature, as this will shift the equilibrium towards the products.
Step-by-step explanation:
To increase the yield of diiodine pentoxide (I₂O₅) in the exothermic equilibrium reaction I₂(g) + 5CO₂(g) ↔ 5CO(g) + I₂O₅(g), the temperature should be decreased. According to Le Chatelier's principle, reducing the temperature will shift the equilibrium toward the products in an exothermic reaction. Hence, lowering the temperature will increase the yield of diiodine pentoxide.
It is important to note that increasing the temperature would add energy to the system, favoring the reactants and not the desired product per the exothermic nature of the reaction. Similarly, decreasing the volume of the reaction vessel will increase the pressure, which would shift the equilibrium towards the side with fewer moles of gas; however, in this case, both sides have the same number of moles of gas, so a change in volume would not affect the yield of I₂O₅.