Question

Which is the most exothermic reaction?

A. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)

B. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)

C. CO2(g) + 2 H2O(l) → CH4(g) + 2 O2(g)

D. CO2(g) + 2 H2O(g) → CH4(g) + 2 O2(g)

Answer 1

Answer:B CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)

If a reaction release heat to surroundings then this  reaction is known as an exothermic reaction

If a reaction absorbs heat from surroundings then this  reaction is known as an endothermic reaction

all the combustion reaction are exothermic.

the reverse reaction of the combustion reaction is an endothermic reaction. So, reactions C and D are endothermic reactions

for A. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)

conversion H₂O(l)  to H₂O(g) is an endothermic process