week 1 defs

Question 1

Exothermic

Answer 1

Heat is given out to the surroundings (the reactants lose energy)

Question 2

Endothermic

Answer 2

Heat is taken in from the surroundings ( the reactants gain energy)

Question 3

Activation energy

Answer 3

The minimum energy required to start a reaction by breaking the bonds

Question 4

Standard conditions

Answer 4

A pressure of 100kpa, a stated temperature, usually 298K (25’C), and a concentration of 1 Mol dm-3 (for reactions with aqueous solutions)

Question 5

Standard enthalpy change of reaction

Answer 5

the enthalpy change that acccompanies a reaction in the molar quantities expressed in a chemical equation (under standard conditions, all reactants and products in their standard states)

Question 6

Standard enthalpy change of formation

Answer 6

the enthalpy change that takes place when one mole of a compound is formed from its constituent elements (in their standard states under standard conditions)

Question 7

Standard enthalpy change of combustion

Answer 7

the enthalpy change that takes place when one mole of a substance reacts comletely with oxygen (under standard states under standard conditions)

Question 8

Average bond enthalpy

Answer 8

the average energy change that takes place when breaking, by homolytic fission, 1 mol of a given type of covalent bond by the molecules of a gaseous species

Question 9

Enthalpy change of neutralisation

Answer 9

The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of a gaseous species

Question 10

Catalyst

Answer 10

speeds up a reaction without being consumed by the overall reaction

Question 11

Dynamic equilibrium

Answer 11

the equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction

Question 12

Le Chatelier’s principle

Answer 12

when a system in dynamic equilibrium is subject to change, the position of equilibrium will shift to minimize the change