In which reaction do the reactants have a lower energy than the products?

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

In which reaction do the reactants have a lower energy than the products? (1) CH4(g)+2O2(g)→CO2(g)+2H2O(g)\mathrm{CH}_4(g)+2\mathrm{O}_2(g)\rightarrow\mathrm{CO}_2(g)+2\mathrm{H}_2\mathrm{O}(g) (2) HBr(g)→H(g)+Br(g)\mathrm{HBr}(g)\rightarrow\mathrm{H}(g)+\mathrm{Br}(g) (3) Na+(g)+Cl−(g)→NaCl(s)\mathrm{Na}^{+}(g)+\mathrm{Cl}^{-}(g)\rightarrow\mathrm{NaCl}(s) (4) NaOH(aq)+HCl(aq)→NaCl(aq)+H2O(l)\mathrm{NaOH}(aq)+\mathrm{HCl}(aq)\rightarrow\mathrm{NaCl}(aq)+\mathrm{H}_2\mathrm{O}(l)

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