Question

For an endothermic reaction, $\Delta H$ is__.

• A. +ve
• B. -ve
• C. 0
• D. none

Answer 1

The correct option is A +ve

Endothermic reactions are the chemical reactions which proceed with the absorption of heat energy.
Consider the reaction $A+B+q\to C+D$.
Here, q is the heat energy absorbed during this exothermic reaction.
The enthalpy change for this reaction is $\Delta H_{rxn}=H_{products}-H_{reactants}=+q$
Positive sign indicates that heat is absorbed in the reaction.
Hence, $H_{reactants}+q=H_{products}$
Thus, in an endothermic reaction, the total enthalpy of reactant is smaller than that of products.
Hence, for an endothermic reaction, H is positive.