Question

Determine the standard enthalpy change for the formation of methane gas (CH4) from its constituent elements (C and H2) given the following standard enthalpy of formation values: ΔHf°(C) = 0 kJ/mol and ΔHf°(H2) = 0 kJ/mol.

Answer 1

To determine the standard enthalpy change for the formation of methane gas  CH4  from its constituent elements  C and H2 , we need to consider the balanced chemical equation for the formation of methane:C  graphite  + 2 H2  g   CH4  g The standard enthalpy change for this reaction  H  can be calculated using the following equation:H =  Hf products  -  Hf reactants Given that the standard enthalpy of formation for both C  graphite  and H2  g  is 0 kJ/mol, we only need to find the standard enthalpy of formation for CH4  g . The standard enthalpy of formation for methane gas  CH4  is -74.8 kJ/mol.Now, we can calculate the standard enthalpy change for the formation of methane:H =  -74.8 kJ/mol  -  0 kJ/mol + 0 kJ/mol  = -74.8 kJ/molTherefore, the standard enthalpy change for the formation of methane gas  CH4  from its constituent elements  C and H2  is -74.8 kJ/mol.