Enthalpy Changes

Question 1

Exothermic

Answer 1

A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants.

Question 2

Endothermic

Answer 2

A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants.

Question 3

Activation energy

Answer 3

Th minimum energy required to start a reaction by the breaking of bonds.

Question 4

Standard conditions

Answer 4

A pressure of 100kPa, a stated temperature and a concentration of 1 mol dm^-3.

Question 5

Enthalpy change of formation

Answer 5

When 1 mole of a compound inits standard state is formed from its constituent elements in their standard states under standard conditions.

Question 6

Enthalpy change of combustion

Answer 6

When 1 mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states.

Question 7

Enthalpy change of reaction

Answer 7

That accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions.

Question 8

Average body enthalpy

Answer 8

Change that takes place when breaking by homolytic fission, 1 mol of a given type o bond in the molecules of a gaseous species.

Question 9

le Chatelier’s principle

Answer 9

When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change.