Using standard heat of formations. (Appendix II in text). Calculate the standard enthalpy change for the combustion of methane.

CH4 (g) + 2 O2 ---�¨ 2CO2(g) + 2H2O (l) ƒ¢H0 = ?

dH = delta H

dHo rxn = (n*dHo products) - (n*dHo reactants)

To calculate the standard enthalpy change for the combustion of methane, you'll need to use the standard heat of formation values for each compound involved. These values are usually provided in a table like Appendix II in the text you mentioned. The standard heat of formation (ΔH°f) is the enthalpy change that occurs when one mole of a compound is formed from its elements in their standard states.

Using the equation you provided:
CH4 (g) + 2 O2 → 2 CO2 (g) + 2 H2O (l)

We'll calculate the standard enthalpy change (ΔH°) by summing up the standard heat of formation values for the products and subtracting the sum of the values for the reactants.

The standard heat of formation values for the compounds in this equation are:
ΔH°f(CH4) = -74.8 kJ/mol
ΔH°f(O2) = 0 kJ/mol (Oxygen is in its standard state)
ΔH°f(CO2) = -393.5 kJ/mol
ΔH°f(H2O) = -285.8 kJ/mol

Now let's calculate the enthalpy change:
ΔH° = (2 * ΔH°f(CO2) + 2 * ΔH°f(H2O)) - (ΔH°f(CH4) + 2 * ΔH°f(O2))
= (2 * -393.5 kJ/mol + 2 * -285.8 kJ/mol) - (-74.8 kJ/mol + 2 * 0 kJ/mol)
= -787 kJ/mol - (-74.8 kJ/mol)
= -787 kJ/mol + 74.8 kJ/mol
= -712.2 kJ/mol

Therefore, the standard enthalpy change (ΔH°) for the combustion of methane is -712.2 kJ/mol.