June 2022

Question 1

5.3. Explain why NaBF4 has a high melting point. (2)

Answer 1

(1) oppositely charged ions or Na+ and BF4– ions

(2) strongly attraction between ions or lots of energy needed to overcome forces of attraction between ions

Question 2

5.4. Explain how the B–N bond is formed.
Name this type of bond formation. (2)

Answer 2

(1) lone pair on N donated (to B)
(2) coordinate or dative covalent

Question 3

6.2. Explain why the first ionisation energies in Group 2 decrease from Magnesium to Barium. (2)

Answer 3

(1) atomic radius increases OR electron removed further from nucleus OR electron in higher energy level OR atoms get larger/more shells

(2) more shielding as group is descended

Question 4

7.3. State what a student would observe in a beaker after a reaction between sodium carbonate and an excess of hydrochloric acid (1)

Answer 4

colourless solution

Question 5

8.3. A student heats a sample of solid hydrated cobalt chloride to obtain completely dry cobalt chloride. Suggest how the student could find out if the sample is completely dry. (2)

Answer 5

(1) heat and weigh

(2) repeat until no change in mass