Which of the following is an exothermic reaction?

Options

A. `N_(2(g))+O_(2(g)) rarr 2NO_(2(g)), Delta H =180.5 kJ`
B. `H_(2)O_((g))+C_((s)) rarr CO_((g))+H_(2(g)), Delta U =131.2 kJ`
C. `2HgO_((s))+180.4 kJ rarr 2Hg_((l))+O_(2(g))`
D. `2Zn_((s))+O_(2(g)) rarr 2ZnO_((s)), Delta U =-693.8 kJ`

Answer

D

Explanation

For exothermic reaction, `Delta H" is "-ve.`
If `Delta n_(g) lt 0, Delta H lt Delta U`.