Module 3 Chapter 9

Question 1

Exothermic

Answer 1

Negative overall enthalpy change; energy released to surroundings.
Making bonds is exothermic

Question 2

Endothermic

Answer 2

Positive overall enthalpy change; energy taken/required from surroundings.
Breaking bonds is endothermic

Question 3

Define activation energy

Answer 3

The minimum energy required for a reaction to take place; the energy required to break bonds in reactants

Question 4

Define standard conditions

Answer 4

25degC/298K, 100kPa, 1 moldm^-3 solutions, reactants and products in standard state (physical state under standard conditions)

Question 5

Define standard enthalphy change of combustion

Answer 5

Enthalpy change associated with complete combustion of one mole of a substance, under standard conditions

Question 6

Define standard enthalpy change of formation

Answer 6

Enthalpy change associated with formation of one mole of a substance from its elements, under standard conditions

Question 7

Define standard enthalpy change of neutralisation

Answer 7

Enthalpy change associated with formation of one mole of water from a neutralisation reaction, under standard conditions

Question 8

Define enthalpy change of reaction

Answer 8

Enthalpy change associated with a stated equation

Question 9

Define average bond enthalpy

Answer 9

Average energy required to break one mole of bonds in one mole of gaseous molecules