Thermochemistry Examples

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

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