Question

A chemist measures the energy change ?H during the following reaction: 2HgO (s) ?2Hg (l) +O2 (g) =?H182.kJ Use the information to answer the following questions. This reaction is...
A. endothermic.
B. exothermic.

Suppose 72.8g of HgO react. Will any heat be released or absorbed?

A. Yes, absorbed.
B. Yes, released.
C. No.

Answer 1

Answer:

A. endothermic.

A. Yes, absorbed.

Explanation:

Let's consider the following thermochemical equation.

2 HgO(s) ⇒ 2 Hg(l) + O₂(g)  ΔH = 182 kJ

The enthalpy of the reaction is positive (ΔH > 0), which means that the reaction is endothermic.

182 kJ are absorbed when 2 moles of HgO react (molar mass 216.59 g/mol). The heat absorbed when 72.8 g of HgO react is:

$72.8g.\frac{1mol}{216.59g} .\frac{182kJ}{2mol} =30.6kJ/mol$