Chemical Energetics

Which reaction has an enthalpy change equal to the standard enthalpy change of formation of propane (C₃H₈)?

• 3C(g) + 8H(g) → C₃H₈(g)

• 3C(s) + 4H₂(g) → C₃H₈(g)

• 3C(s) + 4H₂(g) → C₃H₈(l)

• 3C(g) + 4H₂(g) → C₃H₈(g)

• enthalpy change of formation and positive value for x

• enthalpy change of formation and negative value for x

• enthalpy change of combustion and formation and positive value for x

• enthalpy change of combustion and formation and negative value for x

Which two values are needed to calculate the enthalpy change for the reaction

6PbO(s) + O₂(g) → 2Pb₃O₄(s)

• enthalpy change of combustion of lead and enthalpy change of formation of Pb₃O₄

• enthalpy change of combustion of PbO and enthalpy change of formation of Pb₃O₄

• enthalpy change of formation of PbO and enthalpy change of formation of Pb₃O₄

Which statement describes the standard enthalpy change of the reaction below? All substances are in their standard states.

XeF₆ + 3H₂O → XeO₃ + 6HF

• the enthalpy change when a total of one mole of products is produced

• the enthalpy change when a total of one mole of reactants is reacted

• the enthalpy change when one mole of water reacts

• the enthalpy change when six moles of hydrogen fluoride are produced

The enthalpy change of the neutralisation given below is –114 kJ mol^–1.

2NaOH(aq) + H₂SO₄(aq) → Na₂SO₄(aq) + 2H₂O(l)

By using this information, what is the most likely value for the enthalpy change of the following neutralisation?

Ba(OH)₂(aq) + 2HCl(aq) → BaCl₂(aq) + 2H₂O(l)

• –57 kJ mol^–1

• –76 kJ mol^–1

• –114 kJ mol^–1

• –228 kJ mol^–1

Which statement about enthalpy changes is correct?

• Enthalpy changes of combustion are always positive.

• Enthalpy changes of formation are always positive.

• Enthalpy changes of neutralisation are always negative.

The enthalpy change when one mole of

gaseous atoms is formed from its element under standard conditions.

• enthalpy change of atomisation

• enthalpy change of formation

• 0 kJ mol^–1

• –824 kJ mol^–1

• –1648 kJ mol^–1

• –3296 kJ mol^–1

If standard enthalpy change of atomisation is the enthalpy change when one mole of gaseous atoms is formed from its element under standard conditions, which equation represents standard enthalpy change of atomisation of bromine?

• Br₂(l) → 2Br(g)

• Br₂(g) → 2Br(g)

Which reaction represents enthalpy change of formation?

• 2C(s) + O₂(g) → 2CO(g)

• C(s) + O₂(g) → CO₂(g)