Module 3 - F322

Question 1

Enthalpy

Answer 1

Is the heat content that is stored in a chemical system.

Question 2

Exothermic

Answer 2

Refers to a reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings.

Question 3

Endothermic

Answer 3

Refers to a reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings.

Question 4

Enthalpy profile diagram

Answer 4

Is a diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products.

Question 5

Activation energy

Answer 5

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

Question 6

Standard conditions

Answer 6

Are a pressure of 100kPa, a stated temperature, usually 298K and a concentration of 1.0molddm3

Question 7

Standard state

Answer 7

Is the physical state of a substance under the standard condition of 100kPa and 298K.

Question 8

Standard enthalpy change of reaction

Answer 8

Is the enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states.

Question 9

Standard enthalpy change of combustion

Answer 9

Is the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states.

Question 10

Standard enthalpy change of formation

Answer 10

Is 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 11

Specific heat capacity

Answer 11

Is the energy required to raise the temperature of 1g of a substance by 1 degree.

Question 12

Bond enthalpy

Answer 12

Is the enthalpy change that takes place when breaking by homolytic fission 1 mol of a given bond in the molecules of a gaseous species.

Question 13

Average bond enthalpy

Answer 13

Is the average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species.

Question 14

Hess’ Law

Answer 14

If a reaction can take place by more than one route and the intial and final conditions are the same, the total enthalpy change is the same for each route.

Question 15

Enthalpy cycle

Answer 15

Is a diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’ Law.

Question 16

Rate of reaction

Answer 16

Is the change in concentration of a reactant or a product in a given time.

Question 17

Heterogeneous catalysis

Answer 17

Is catalysis of a reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases whilst the catalyst is a solid.

Question 18

Homogeneous catalyst

Answer 18

Is catalysis of a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state.

Question 19

Boltzmann distribution

Answer 19

Is the distribution of energies of molecules at a particular temperature, often shown as a graph.

Question 20

Dynamic equilibrium

Answer 20

Is 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 21

Le Chatelier’s principle

Answer 21

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