Thermochemistry Examples

Enthalpy and Heat Transfer

Example

Basic Calorimetry Calculation

A civil engineer is designing a cooling system for a massive concrete pour to prevent thermal cracking. Calculate the amount of heat energy (qq) required to cool a 5000kg5000 \, \text{kg} block of concrete from 40.0C40.0^\circ\text{C} to 20.0C20.0^\circ\text{C}. The specific heat capacity (cc) of this concrete mix is 0.880J/(gC)0.880 \, \text{J/(g} \cdot ^\circ\text{C)}.

Step-by-Step Solution

0 of 4 Steps Completed
1

Example

Hess's Law: Combustion of Methane

Calculate the standard enthalpy of combustion (ΔHc\Delta H^\circ_c) for methane (CH4CH_4) given the standard enthalpies of formation (ΔHf\Delta H^\circ_f) for the reactants and products: ΔHf(CO2(g))=393.5kJ/mol\Delta H^\circ_f(CO_2(g)) = -393.5 \, \text{kJ/mol} ΔHf(H2O(l))=285.8kJ/mol\Delta H^\circ_f(H_2O(l)) = -285.8 \, \text{kJ/mol} ΔHf(CH4(g))=74.8kJ/mol\Delta H^\circ_f(CH_4(g)) = -74.8 \, \text{kJ/mol}

Step-by-Step Solution

0 of 4 Steps Completed
1