Carbon and oxygen react to give carbon dioxide.The reaction of 4.49 g C(s)with 9.21 g O₂(g)releases −113.2 kJ of heat.What is the enthalpy of formation of CO₂(g)?

Question

Quizplus · Accepted Answer

The enthalpy of formation ($\Delta H_f^\circ$) of a compound is the heat change that results when one mole of the compound is formed from its elements in their standard states. For carbon dioxide ($CO_2$), this process can be represented by the equation: $C(s) + O_2(g) \rightarrow CO_2(g)$. Given that 4.49 g of carbon (which is about 0.374 moles, since the molar mass of carbon is approximately 12.01 g/mol) reacts with oxygen to release -113.2 kJ of heat, we need to find the heat released for the formation of 1 mole of $CO_2$. Since the reaction as given involves the formation of 1 mole of $CO_2$ from its elements, and the given heat release is for the amount of carbon used (not necessarily 1 mole), we adjust the heat release to per mole of $CO_2$ formed. The calculation directly leads to the enthalpy of formation of $CO_2$, which is a standard value of approximately -393 kJ/mol, indicating that choice A is correct.

Carbon and Oxygen React to Give Carbon Dioxide