Sucrose, C12 H22 O11, is common table sugar. The enthalpy...

Sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$, is common table sugar. The enthalpy change at $25^{\circ} \mathrm{C}$ and 1 atm for the complete burning of $1 \mathrm{~mol}$ of sucrose in oxygen to give $\mathrm{CO}_{2}(g)$ and $\mathrm{H}_{2} \mathrm{O}(l)$ is $-5641 \mathrm{~kJ}$. From this and from data given in Table $6.2$, calculate the standard enthalpy of formation of sucrose.

Key Concepts

Balanced Chemical Equations

Balancing chemical equations ensures that the law of conservation of mass is adhered to by having the same number of atoms for each element on both sides of the reaction. This is essential in thermochemical calculations because accurate stoichiometric coefficients determine how much energy is associated with each reactant and product.

Thermochemical Equations

These are balanced chemical equations that include the enthalpy change for the reaction, allowing the explicit inclusion of energy changes in chemical calculations. They serve as a critical tool in thermochemistry by linking stoichiometry with energy changes.

Standard Enthalpy of Formation

This is the heat change that occurs when one mole of a compound is formed from its elements in their standard states. It serves as a baseline for comparing the energy content of compounds, as it relates directly to the stability and energy stored in chemical bonds and helps in calculating the overall energy change of reactions.

Standard Enthalpy of Combustion

This refers to the amount of energy released when one mole of a substance is completely burned in oxygen under standard conditions. It provides a measure of the efficiency of the substance as a fuel and is used to compare the energy outputs of different compounds when they undergo oxidation.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is independent of the pathway taken, meaning that heat changes can be added together from individual steps to yield the overall change. This principle is fundamental in calculating unknown enthalpy changes by combining known related reactions.

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