3.3. Enthalpy

Question 1

What is Enthalpy?

Answer 1

Enthalpy is a measure of the chemical energy in a substance.

Question 2

What is enthalpy of combustion?

Answer 2

Question 3

What does Hess’ Law state?

Answer 3

Hess’s law states that the enthalpy change for a chemical reaction is independent of the route taken.

Question 4

What is molar bond enthalpy?

Answer 4

Molar bond enthalpy is the energy required to break one mole of bonds in a diatomic molecule

Question 5

What is meant by mean molar bond enthalpy?

Answer 5

Mean molar bond enthalpy is the average energy required to break one mole of bonds, for a bond that occurs in a number of compounds.

Question 6

What is meant by the molar volume of a gas?

Answer 6

The molar volume (litres mol-1 ) is the volume occupied by one mole of any gas at a certain temperature and pressure

Question 7

How do molar volumes of gases compare?

Answer 7

The molar volume is the same for all gases at the same temperature and pressure

Question 8

Why might it be important in industry to know if a reaction is exothermic or endothermic?

Answer 8

• In industry, exothermic reactions may require heat to be removed to prevent the temperature rising.
• • In industry, endothermic reactions may incur costs in supplying heat energy in order to maintain the reaction rate.