Jan 2019

Question 1

1.3. Predict whether the atomic radius of 40Ca is larger than, smaller than, or same as the atomic radius of 42Ca. Explain. (2)

Answer 1

(1) Same
(2) Same number of protons and electrons

Question 2

2.1. Explain, in terms of intermolecular forces, why NH3 has a higher boiling point than PH3. (3)

Answer 2

(1) NH3 has H bonding between molecules
(2) PH3 has vdw forces between molecules
(3) Hydrogen bonds are stronger or strongest IMF

Question 3

2.2. Explain, in terms of intermolecular forces, why AsH3 has a higher boiling point than PH3. (2)

Answer 3

(1) AsH3 is a bigger molecule or has more electrons
(2) So more or stronger vdw between molecules

Question 4

4.5. State how solid sodium chloride can be obtained from the mixture of products: Cl2 (g) + H2O (l) + NaCl (aq).
(1)

Answer 4

evaporation

Question 5

4.6. Suggest one precaution a chemist should take when making chlorine gas. (1)

Answer 5

Use a gas mask or a fume cupboard

Question 6

7.2. Explain why the first ionisation energy of aluminium is less than the first ionisation energy of magnesium. (2)

Answer 6

(1) Electron removed from a (3)p orbital
(2) Which is higher in energy (so more easily lost)

Question 7

7.3. Identify the element in Period 3 with the largest atomic radius. Explain. (3)

Answer 7

(1) Sodium
(2) Smallest number of protons
(3) All electrons in period 3 elements enter the same (3rd) principal energy level OR elements in period 3 have similar shielding