Question

Which reaction is exothermic?
a- CH4 + 2O2 Right arrow. CO2 + 2H2O + 891 kJ
b- NH4NO3 + H2O + 25 kJ Right arrow. NH4+(aq) + NO3-(aq)
c -2H2O + 286 kJ Right arrow. 2H2 + O2
d- N2 + O2 + 181 kJ Right arrow. 2NO

Answer 1

Answer:

option a

Explanation:

The combustion of methane or octane is exothermic; it releases energy. CH4 + 2 O2 → CO2 + 2 H2O + energy The energies of the products are lower than the energiies of the reactants.

Answer 2

An exothermic reaction is a reaction that releases heat, meaning that the products have less energy than the reactants. Among the given reactions, the exothermic reaction is: CH4 + 2O2 → CO2 + 2H2O + 891 kJ.(Option A)

a. CH4 + 2O2 → CO2 + 2H2O + 891 kJ

• This reaction releases 891 kJ of energy, indicating that it is exothermic.

b. NH4NO3 + H2O + 25 kJ → NH4+(aq) + NO3-(aq)

• This reaction absorbs 25 kJ of energy, indicating that it is endothermic.

c. 2H2O + 286 kJ → 2H2 + O2

• This reaction also releases energy, but it is not as exothermic as the first reaction. Moreover, the reaction requires a specific condition (i.e., energy input) to occur, making it less spontaneous.

d. N2 + O2 + 181 kJ → 2NO

• This reaction also releases energy, but it is not as exothermic as the first reaction. Moreover, the reaction is not as common as the first reaction.

In summary, the correct answer is (a) CH4 + 2O2 → CO2 + 2H2O + 891 kJ, which is exothermic and releases 891 kJ of energy.

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