Question

Find the standard enthalpy change for the formation reaction of methane gas (CH4) from its elements in their standard states, given the following standard enthalpy of formation values: ΔHf°[CH4] = -74.81 kJ/mol ΔHf°[H2] = 0 kJ/mol ΔHf°[C(graphite)] = 0 kJ/mol

Answer 1

The standard enthalpy change for the formation reaction of methane gas  CH4  from its elements in their standard states can be found using the given standard enthalpy of formation values.The formation reaction of methane gas  CH4  from its elements in their standard states is:C graphite  + 2H2 g   CH4 g To find the standard enthalpy change  H  for this reaction, we can use the following equation:H = Hf products  - Hf reactants In this case, the only product is CH4, and the reactants are C graphite  and H2. We are given the standard enthalpy of formation values for each of these substances:Hf[CH4] = -74.81 kJ/molHf[H2] = 0 kJ/molHf[C graphite ] = 0 kJ/molNow we can plug these values into the equation:H =  -74.81 kJ/mol  -  0 kJ/mol + 0 kJ/mol H = -74.81 kJ/molSo, the standard enthalpy change for the formation reaction of methane gas  CH4  from its elements in their standard states is -74.81 kJ/mol.