Which of the following is an endothermic reaction?

Options

A. `C_(2)H_(2(g))+2H_(2(g)) rarr C_(2)H_(6(g)), Delta H =-314.0 kH`
B. `2HgO_((s)) rarr 2Hg_((l))+O_(2(g)), Delta U =180.8 kJ`
C. `2Zn_((s))+O_(2(g)) rarr 2ZnO_((s)), Delta U =-693.8 kJ`
D. `C_((s))+O_(2(g)) rarr CO_(2(g))+393.6 kJ`

Answer

B

Explanation

(b) `2HgO_((s)) rarr 2Hg_((l))+O_(2(g)) Delta H=180. 8 kJ`
This reaction is endothermic, as `Delta H` is + ve.
(d) `C_((s))+O_(2(g)) rarr CO_(2(g))+393.6 kJ`
This reaction is not endothermic, as for this q (heat evolved) is + ve. It is exothermic.