Question

Sure, here's a problem:Calculate the standard enthalpy change for the combustion of methane gas (CH4) using the following information:Formation of CO2: -393.5 kJ/molFormation of H2O: -285.8 kJ/molFormation of CH4: -74.8 kJ/mol

Answer 1

To calculate the standard enthalpy change for the combustion of methane gas  CH4 , we need to consider the balanced chemical equation for the combustion reaction:CH4  g  + 2 O2  g   CO2  g  + 2 H2O  g Now, we can use Hess's Law to determine the standard enthalpy change for the reaction. Hess's Law states that the enthalpy change for a reaction is equal to the sum of the enthalpy changes for the formation of the products minus the sum of the enthalpy changes for the formation of the reactants.H_combustion = [H_formation CO2  + 2 * H_formation H2O ] - [H_formation CH4  + 2 * H_formation O2 ]Since O2 is in its standard state, its enthalpy of formation is 0 kJ/mol. Now, we can plug in the given values:H_combustion = [ -393.5 kJ/mol  + 2 *  -285.8 kJ/mol ] - [ -74.8 kJ/mol  + 2 *  0 kJ/mol ]H_combustion =  -393.5 - 571.6 + 74.8  kJ/molH_combustion = -890.3 kJ/molThe standard enthalpy change for the combustion of methane gas  CH4  is -890.3 kJ/mol.