Unit 3 : Chemical Energy

Question 1

Enthalpy

Answer 1

Enthalpy (H) is a measure of the energy stored in a chemical

Question 2

Exothermic Reactions

Answer 2

A reaction or process that releases heat energy is described as exothermic.

In industry, exothermic reactions may require heat to be removed to prevent the temperature from rising.

Question 3

Endothermic Reactions

Answer 3

A reaction or process that takes in heat energy is described as endothermic.

In industry, endothermic reactions may incur costs in supplying heat enerrgy in order to main the reaction rate.

Question 4

Enthalpy of combustion

Answer 4

The enthalpy of combustion is defined as the enthalpy change that occurs when one mole of a substance is burned completly in oxygem

Question 5

Hess’s Law

Answer 5

Hess’s law states that the enthalpy change for a chemical reaction is independant of the route taken, providing the starting point and the finsishing poitn is the same for both routes.

Question 6

The molar bond enthalpy

Answer 6

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

Question 7

Mean Molar Bond enthalpy

Answer 7

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