An endothermic reaction becomes exothermic when a catalyst is added into the reaction mixture.

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Consider the statement: 'An endothermic reaction becomes exothermic when a catalyst is added into the reaction mixture.'
Option 1: True. This option asserts that a catalyst can flip the heat flow direction of a reaction. In reality, catalysts do not alter the overall enthalpy change (ΔH) of a reaction; they only provide an alternative reaction pathway with a lower activation energy. Therefore, the thermodynamic character of the reaction—whether it is endothermic or exothermic—remains unchanged by the presence of a catalyst.
Option 2: False. This is the correct characterization of how catalysts work. A catalyst increases the rate at which equilibrium is reached (or the rate of conversion) by lowering the activation energy of the reaction, but it does not change the total energy absorbed or released during the process. Consequently, an endothermic reaction stays endothermic, and an exothermic reaction stays exothermic, with or without a catalyst. It only speeds up the rate, not the thermodynamic outcome.
Additional nuance: If temperature changes accompany catalysis in a system, you might observe different reaction rates or shifts in equilibrium positions due to temperature dependencies, but the fundamental ΔH of the reaction path remains the same. The catalyst cannot convert an endothermic process into an exothermic one, nor vice versa.

CHM1051 MUM S1 2025 Week 12: Weekly quiz (1%)

An endothermic reaction becomes exothermic when a catalyst is added into the reaction mixture.

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