The bond enthalpy of a carbon-hydrogen bond in methane CH4 can be determined using experimental data. Bond enthalpy is the energy required to break a bond and is usually reported in units of kJ/mol.The standard enthalpy of formation for methane Hf is -74.8 kJ/mol. This value represents the energy change when one mole of methane is formed from its constituent elements carbon and hydrogen in their standard states. The reaction can be represented as:C graphite + 2 H2 g CH4 g Since there are four carbon-hydrogen bonds in methane, we can calculate the average bond enthalpy for a single C-H bond by dividing the total enthalpy change by the number of bonds formed:Hf CH4 = 4 C-H bond enthalpyTo find the enthalpy change for the formation of one mole of carbon and two moles of hydrogen, we need to consider the standard enthalpy of formation for hydrogen gas H2 , which is 0 kJ/mol since it is an element in its standard state . The standard enthalpy of formation for graphite carbon is also 0 kJ/mol for the same reason.Now, we can rearrange the equation to solve for the C-H bond enthalpy:C-H bond enthalpy = Hf CH4 / 4C-H bond enthalpy = -74.8 kJ/mol / 4C-H bond enthalpy -18.7 kJ/molHowever, this value is negative because it represents the energy released when the bond is formed. The bond enthalpy, which is the energy required to break the bond, will be the positive value of this number:C-H bond enthalpy 18.7 kJ/molTherefore, the bond enthalpy of the carbon-hydrogen bond in methane CH4 is approximately 18.7 kJ/mol. Keep in mind that this value is an average bond enthalpy, as individual bond energies can vary depending on the specific molecule and its environment.