Question

For a reaction: $C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)}$ what is the relation between enthalpy of reaction ($\Delta H_{R}$), enthalpy of formation of $CO_{2}(\Delta H_{f})$ enthalpy of combustion of carbon ($\Delta H_{comb}$)?

• A. $\Delta H_{R} > \Delta H_{f} = \Delta H_{comb}$
• B. $\Delta H_{R} = \Delta H_{f} = \Delta H_{comb}$
• C. $\Delta H_{R} = \Delta H_{f} + \Delta H_{comb}$
• D. $\Delta H_{R} = 2 \times \Delta H_{f}$

Answer 1

Answer: (B)

$\Delta H_{R} = \Delta H_{f} = \Delta H_{comb}$

Answer 2

: Since the reaction shows combustion of one mole of carbon, $\Delta H_{reaction}$ is enthalpy of combustion since 1 mole of $CO_{2}$is formed $\Delta H_{reaction}$is also the enthalpy of formation of $CO_{2.}$