June 2018

Question 1

7.1. Define standard enthalpy of formation (2)

Answer 1

(1) enthalpy (or heat energy) change when 1 mol of a substance
(2) is formed from its elements when all substances in their standard states

Question 2

7.2. State Hess’s Law (1)

Answer 2

(1) enthalpy change (or enthalpy of reaction) is independent of route

Question 3

8.4. Suggest why magnesium is ductile (can be stretched into wires). (1)

Answer 3

(1) layers of atoms/ions slide over one another

Question 4

8.5. State 2 observations made when magnesium reacts with steam (2)

Answer 4

(1) white powder/ash/ solid
(2) (bright) white light