Classify each of the following as an exothermic or an endothermic reaction:

a. C3H8 (g) + O2 (g) → CO2 (g) + H2O (g) + 2220 kj

b. 2 Na (s) + Cl2 (g) → 2 NaCl (s) + 819 kj

c. PCl5 (g) + 67kj → PCl3 (g) + Cl2 (g)

Equation a. C3H8 (g) + O2 (g) → CO2 (g) + H2O (g) + 2220 kj

is endothermic. + 2220 kj

Equation b. 2 Na (s) + Cl2 (g) → 2 NaCl (s) + 819kJ

is also endothermic since the overall energy change is positive. + 819kJ

The equation c. PCl5 (g) + 67kj → PCl3 (g) + Cl2 (g) is endothermic since it requires anergy to proceed.

Reaction A) is exothermic

Reaction B) is exothermic

Reaction C) is endothermic.

Explanation:

Hi, by definition an exothermic reaction is the one that generates heat as it occurs. An endothermic reaction on the other hand, consumes heat from the environment as it happens.

This can be seen, when energy is put as a reactant in the equation. When it appears as a procuct the reaction is exothermic.

Being all that said:

Reaction A) is exothermic Reaction B) is exothermic Reaction C) is endothermic.