which reaction is exothermic?\no ch4 + 2o2→co2 + 2h2o + 891 kj\no nh4no3 + h2o + 25 kj→nh4+(aq) +…
which reaction is exothermic?\no ch4 + 2o2→co2 + 2h2o + 891 kj\no nh4no3 + h2o + 25 kj→nh4+(aq) + no3-(aq)\no 2h2o + 286 kj→2h2 + o2\no n2 + o2 + 181 kj→2no
Answer
Explanation:
Step1: Recall exothermic reaction definition
An exothermic reaction releases energy. In chemical - reaction equations, energy is shown as a product on the right - hand side of the equation.
Step2: Analyze each option
- For $\mathrm{CH_4 + 2O_2\rightarrow CO_2 + 2H_2O+891\ kJ}$, energy ($891\ kJ$) is a product, so it is exothermic.
- For $\mathrm{NH_4NO_3 + H_2O + 25\ kJ\rightarrow NH_4^+(aq)+NO_3^-(aq)}$, energy is a reactant, so it is endothermic.
- For $\mathrm{2H_2O + 286\ kJ\rightarrow 2H_2+O_2}$, energy is a reactant, so it is endothermic.
- For $\mathrm{N_2 + O_2+181\ kJ\rightarrow 2NO}$, energy is a reactant, so it is endothermic.
Answer:
$\mathrm{CH_4 + 2O_2\rightarrow CO_2 + 2H_2O + 891\ kJ}$