What energy change is associated with the reaction to obtain one mole of H2 from one mole of water vapor? The balanced equation is 2 H2O(g) -> 2 H2(g) + O2(g)and the relevant bond energies are
H-H : 436 kJ/mol; H-O : 467 kJ/mol;
O-O : 146 kJ/mol; O=O : 498 kJ/mol.
1. +249 kJ
2. −436 kJ
3. +425 kJ
4. −425 kJ
the answer is 246
It appears to me that we must break 4 OH bonds for the two moles H2O and form 2 H-H bonds and 2 O-O bonds. The difference between (sum bond energies reactants)-(sum bond energies products) = delta H rxn for 2 moles H2O and 2 moles H2. Therefore, divide that number by 2. Check my thinking.
To determine the energy change associated with the given reaction, we need to calculate the energy required to break the bonds in one mole of water vapor and the energy released when the new bonds form in one mole of H2.
First, let's calculate the energy required to break the bonds in one mole of water vapor (2 H2O(g)):
(2 H-O) x 467 kJ/mol = 934 kJ
(1 O=O) x 498 kJ/mol = 498 kJ
Total energy required = 934 kJ + 498 kJ = 1432 kJ
Next, let's calculate the energy released when the new bonds form in one mole of H2 (2 H2(g)):
(4 H-H) x 436 kJ/mol = 1744 kJ
Finally, to calculate the overall energy change, we subtract the energy required to break the bonds from the energy released when the new bonds form:
Energy change = Energy released - Energy required
Energy change = 1744 kJ - 1432 kJ
Energy change = +312 kJ/mol
Therefore, the correct answer is:
1. +249 kJ
Explanation: The energy change associated with the reaction to obtain one mole of H2 from one mole of water vapor is approximately +249 kJ.