Question

Calculate the heat of combustion for the following reactions from the standard enthalpies:

a) Exothermic reactions
b) Endothermic reactions
c) Isobaric reactions
d) Isometric reactions

Answer 1

In order to determine whether a chemical reaction is exothermic or endothermic, we can look at the change in enthalpy of the reaction. If the reaction releases heat to the surroundings, it is exothermic. If the reaction absorbs heat from the surroundings, it is endothermic.

Step-by-step explanation:

In order to determine whether a chemical reaction is exothermic or endothermic, we can look at the change in enthalpy (or heat) of the reaction. If the reaction releases heat to the surroundings, it is exothermic. If the reaction absorbs heat from the surroundings, it is endothermic.

For example, in reaction a:

2H₂(g) + O₂(g) → 2H₂O(l) + 135 kcal

The reaction releases 135 kcal of heat, so it is exothermic.

On the other hand, in reaction b:

N₂(g) + O₂(g) + 45 kcal → 2NO(g)

The reaction absorbs 45 kcal of heat, so it is endothermic.