Inv 8 Exp 1 - Bond Energies - Day 1

2H₂O --> 2H₂ + O₂

The enthalpy of reaction for the electrolysis of water is +506 kJ/mol for each mol of O2 produced. Select all statements that are true about this reaction

• The reaction releases a lot of heat to the environment

• The bond energy of all bonds on the products is higher than the bond energy of the bonds of the reactants.

• It takes energy to get H₂ from water via electrolysis

• The bond energy of all bonds on the reactant is higher than the bond energy of the bonds of the product.

N₂ + 2O₂ --> N₂O₄

How much energy does it take to break the bonds of the reactants needed to make one mole of N₂O₄? The bond energy between N atoms in N₂ is 945 kJ/mol and between O atoms in O₂ is 498 kJ/mol

• 1443 kJ

• 1941 kJ

• -1443 kJ

• 447 kJ

The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, when one mole of O=O is produced in the reaction below?

2H-O-O-H(g) → 2H-O-H(g) + O=O(g)

• -204 kJ

• Can't be calculated. We need the bond energy of H-O.

• -350 kJ

• 204 kJ

For the reaction 2H₂(g) + O₂(g) → 2H₂O(g) the bond enthalpies (in kJ/mol) are

H-H = x, O=O = y, O-H = z

Which calculation will give the value, in kJ/mol, of ΔH for the reaction?

• 2x + y - 2z

• 4z - 2x - y

• 2x + y - 4z

• 2z - 2x - y

The following equation shows the formation of magnesium oxide from magnesium metal. Which statement is correct for this reaction?

2Mg(s) + O₂(g) → 2MgO(s) ΔH = -1204 kJ

• 1204 kJ of energy are released for every mole of magnesium reacted

• 602 kJ of energy are absorbed for every mole of magnesium oxide formed

• 602 kJ of energy are released for every mole of oxygen reacted

• 1204 kJ of energy are released for every two moles of magnesium oxide formed

When new chemical bonds form, energy ____________.

• is taken into the system from the environment.

• is released from the system to the environment.

• stays the same in the system.

What is still confusing? How can I help?