3.3 Chemical Energy

Question 1

Enthalpy

Answer 1

Enthalpy is a measure of the chemical energy in a substance

Question 2

Exothermic reactions in industry

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 rising

Question 3

Endothermic reactions in industry

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 energy in order to maintain the reaction rate

Question 4

How to calculate the Enthalpy change associated with a reaction?

Answer 4

From the quantity of heat energy released.

It can be calculate using : Eh=c x m x change in temp

Question 5

Enthalpy of combustion

Answer 5

The Enthalpy of combustion of a substance is the Enthalpy change when one mole of the substance burns completely in oxygen

Question 6

Hess’s law

Answer 6

States that the Enthalpy change for a chemical reaction is independent of the route taken

Question 7

Molar and mean molar bond Enthalpy

Answer 7

The energy required to break one mole of bonds in a diatomic molecule.

A 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 8

What can bond enthalpies be used to estimate?

Answer 8

The Enthalpy change occurring for a gas phase reaction, by calculating the energy required to break binds in the reactants and the energy released when new binds are formed in the products