# AP Chem

posted by .

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

• AP Chem -

2 H2O(g) -> 2 H2(g) + O2(g)

H2O(g) -> H2(g) + 1/2 O2(g)
1mol 1 mol 1/2 mole
each mole H2O has 2 moles of O-H bonds to break (energy requiring) = 2 x 467 = 934 kJ

Each mole H2 has 1 mole H-H bonds to make (energy releasing) = 436 kJ
Each mole O2 has 1 mole O=O bonds to make. So 1/2 mole = 1/2 x 498 = 249 kJ

Energy required in bond breaking = 934 kJ
Energy released in bond making = 436 + 249 = 685 kJ

Balance needed = 934 - 685 = 249 kJ
So Delta H = +249kJ

## Similar Questions

1. ### science

1.The energy associated with the absorption of a photn of wavelength 4.26 micrometers is ______________?
2. ### Ap Chem

If in an experiment we're working with Mg, HCl acid, and H20. We stick the magnesium in the acid mixed with water and the Mg dissolves. One of the products is hydrogen gas. If the water in the tube is evaporated, the other product, …
3. ### chem

One mole of H2O(g) at 1.00 atm and 100.°C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100.°C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature …
4. ### CHEMISTRY

One mole of H2O(g) at 1.00 atm and 100 degrees C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100 degrees C, 40.66 kJ of heat is released. If the density of H2O(l) at this …
5. ### Chemistry

One mole of H2O(g) at 1.00 atm and 100.°C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100.°C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature …
6. ### AP Chem

What energy change is associated with the reaction to obtain one mole of H2 from one mole of water vapor?
7. ### College Chemistry

One mole of H2O(g) at 1.00 atm and 100.°C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100.°C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature …
8. ### chemistry

One mole of H2O(g) at 1.00 atm and 100.°C occupies a volume of 30.6 L. When one mole of H2O(g) is condensed to one mole of H2O(l) at 1.00 atm and 100.°C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature …
9. ### Thermodynamics

The initial state consists of a closed system containing one mole of super-heated liquid water at 115°C and 1 atmosphere pressure. The immediate surroundings are also at 115°C and 1 atmosphere pressure. The change in state is described …
10. ### Thermodynamics

The initial state consists of a closed system containing one mole of water (liquid) at 85°C and 1 atmosphere pressure. The immediate surroundings are also at 85°C and 1 atmosphere pressure. The change in state is described as this …

More Similar Questions