One renewable energy fuel source is hydrogen. Hydrogen fuel cells use the chemical energy of hydrogen to cleanly and efficiently produce electricity. However, hydrogen is usually “tied-up” in other...

One renewable energy fuel source is hydrogen. Hydrogen fuel cells use the chemical energy of hydrogen to cleanly and efficiently produce electricity. However, hydrogen is usually “tied-up” in other molecules such as hydrocarbons and must be harvested. The two main ways this is done is by (1) “splitting” water to make hydrogen gas or (2) reforming natural gas (methane). However, process 2 means we are using fossil fuels (non-renewable energy sources) to create renewable energy.

(1) H₂O(l) → H₂(g) + ½ O₂(g)                      ΔH_rxn = +285.8 kJ/mol

(2) CH₄(g) + 2H₂O(g) → CO₂(g) + H₂(g)    ΔH_rxn = _______ kJ/mol

Using the standard enthalpies of formation in the table below and equation 7.15 (Tro pg. 292), calculate ΔH_rxn
for reaction 2. (I have a included an image of this equation)

b. compare the reaction enthalpies for splitting water and for reforming natural gas.