Defintions Mod 3

Question 1

What is meant by the term periodicity

Answer 1

• Repeating trends across a period

Question 2

What is meant by the term metallic bonding

Answer 2

• Strong electrostatic attraction between positive metal ions in a lattice and delocalised electrons

Question 3

What is meant by the term disproportionation

Answer 3

• Simultaneous oxidation and reduction of the same element

Question 4

What is meant by the term standard enthalpy change of reaction

Answer 4

• The enthalpy change when the numbers of moles of the substances in the balanced equation react under standard conditions

Question 5

What is meant by the term enthalpy change of formation

Answer 5

• The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions

Question 6

What is meant by the term enthalpy change of combustion

Answer 6

• The enthalpy change when one mole of a substance reacts completely with oxygen under standard conditions.

Question 7

What is meant by the term enthalpy change of neutralisation

Answer 7

• Enthalpy change of the formation of 1 mol water from neutralization

Question 8

What is meant by the term average bond enthalpy

Answer 8

• Enthalpy change on the breaking of 1 mol of covalent bonds in a gaseous molecule.

Question 9

What is meant by the term exothermic

Answer 9

• If the reaction mixture loses the energy to its surroundings, then the reaction is exothermic and delta H is negative

Question 10

What is meant by the term endothermic

Answer 10

• If the reaction mixture gains energy from its surroundings, the reaction is endothermic and delta is positive

Question 11

What is meant by the term Hess’ Law

Answer 11

• If a reaction can take place by more than one route, the overall enthalpy change for each route is the same provided that the initial and final conditions are the same.

Question 12

What is meant by the term catalyst

Answer 12

• Increases the rate of a reaction without being consumed by the overall reaction by providing an alternate route with a lower activation energy

Question 13

What is meant by the term heterogeneous catalysts

Answer 13

• The catalyst is in a different physical state to the reactants

Question 14

What is meant by the term homogeneous catalysts

Answer 14

• The catalyst is in the same physical state as the reactants

Question 15

What is meant by the term dynamic equilibrium

Answer 15

• 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 16

What is meant by the term le Chatelier’s principle

Answer 16

• The position of a dynamic equilibrium shifts to minimise the effect of any change

Question 17

Standard conditions

Answer 17

• 100kPa (1 atm), 298K (25*C)