Question

Based on the following reactions

C(graphite) $+O_{2}\left(\right.g\left.\right) \rightarrow CO_{2}\left(\right.g\left.\right);\Delta H=-394$ KJ/mol …(i)

$2CO\left(\right.g\left.\right)+O_{2}\left(\right.g\left.\right) \rightarrow 2CO_{2}\left(\right.g\left.\right);\Delta H=-569$ KJ/mol …(ii)

The heat of formation of CO will be

• A. +109.5 kJ
• B. +219 kJ
• C. -109.5 KJ
• D. -219 KJ

Answer 1

Answer: (C)

$E_{C}+E_{O_{2}} \rightarrow E_{C O_{2}}+394$

$E_{C O_{2}}=-394$

$2E_{C O}+E_{O_{2}} \rightarrow 2E_{C O_{2}}+569$

$2E_{C O}=2E_{C O_{2}}+569=2E_{C O_{2}}+569$

$=2\times -394+569=-219$

$\therefore \, \text{E}_{\text{CO}} \, \text{=} \, - \text{109} \text{.5} \, \text{kJ}$