Question

For the following two reactions:
(i) $C{H}_4\left(g\right)+2O_2\left(g\right)\to C{O}_2\left(g\right)+2H_{2}O\left(g\right);\Delta H=-890.4kJ$
(ii) $2HgO\left(s\right)\to 2Hg\left(l\right)+O_2\left(g\right);\Delta H=+181.6kJ$
Which one of the following statements is correct?

• A. Both of them are exothermic
• B. Both of them are endothermic
• C. (i) is exothermic and (ii) is endothermic
• D. (i) is endothermic and (ii) is exothermic

Answer 1

Answer: (C)

(i) is exothermic and (ii) is endothermic

For an exothermic reaction ($\Delta H=$negative)

For an endothermic reaction ($\Delta H=$positive)

(i) is exothermic and (ii) is endothermic.