The enthalpy of combustion of solid carbon to form carbon...

The enthalpy of combustion of solid carbon to form carbon dioxide is $-393.7 \mathrm{kJ} / \mathrm{mol}$ carbon, and the enthalpy of combustion of carbon monoxide to form carbon dioxide is $-283.3 \mathrm{kJ} / \mathrm{mol}$ CO. Use these data to calculate $\Delta H$ for the reaction $$2 \mathrm{C}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}(g)$$

Key Concepts

Reaction Enthalpy Calculation using Combustion Data

Calculating the enthalpy change for a reaction using combustion data involves setting up a Hess's Law cycle where the known enthalpies of combustion of the substances are used as building blocks. By appropriately manipulating these known reactions, one can derive the enthalpy change for the overall reaction of interest.

Standard Enthalpy Changes

Standard enthalpy changes refer to the heat change associated with a reaction under standard conditions (typically 298 K and 1 atm). These values provide a common reference point, allowing comparisons and the use of tabulated combustion and formation data in thermodynamic calculations.

Hess's Law

Hess's Law states that the total enthalpy change for a chemical reaction is independent of the pathway taken from reactants to products. This principle allows one to calculate the enthalpy change of a reaction by combining other reactions with known enthalpy changes, typically by reversing, adding, or multiplying these reactions to obtain the desired overall reaction.

Enthalpy of Combustion

The enthalpy of combustion is the energy released as heat when one mole of a substance completely reacts with oxygen to produce combustion products, typically carbon dioxide and water in the case of organic compounds. This value is useful in determining energy changes in processes involving burning or oxidation.

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