Question

Burning 2.00 mol of hydrogen releases 483.6 kJ of energy. Determine how much energy, in kilojoules, must be supplied to convert 5.00 mol of water vapor into hydrogen gas and oxygen gas.

Answer 1

2H2(g) + O2(g) --> 2H2O(g) + 483.6 kJ.
You want to go backwards with 5.00 mols H2O vapor instead of 2.00 mols.
483.6 kJ x (5.00/2.00) = ?

Answer 2

1209