June 2018 AS1

Question 1

Q11 a)vi) Chlorine monoxide cannot be collected over water as it is very soluble in water, with a solubility of 143 g in 100 cm^3 at room temperature and pressure. Explain how you could show that chlorine monoxide is very soluble in water. [4]

Answer 1

Either
Fill a test tube with chlorine monoxide [1] seal the end of the test tube [1] invert in a beaker of water [1] open the test tube to see how far the water rises [1]
Or
Bubble through H2O [1]
stated volume of H2O/until bubbles appear [1]
measured using a physical property, e.g. colour, pH, density, mass, volume, forming precipitate with AgNO3(aq) [2]

Question 2

Q12 b)iii) Explain how you would show that the orange solution contains ammonium ions.

Answer 2

Heat with sodium hydroxide solution [1]
moist indicator paper/litmus/red litmus/UI paper [1]
turns blue [1]

Question 3

Q12 c) The nitrogen given off in the reaction consist of two isotopes, nitrogen-14 and nitrogen-15. The percentage abundance of nitrogen-14 is 99.632%.

iii) Calculate the relative atomic mass of nitrogen to three decimal places.
iv) Explain why there is a difference between the calculated relative atomic mass and the one provided in the data sheet.

Answer 3

(iii) 99.632 × 14 = 1394.848 0.368 × 15 = 5.52
= 1400.368 = 14.004 [2]
(iv) The RAMs in the table are listed as whole numbers (exception of chlorine) [1]

Question 4

Q12 (d) The dichromate ion is a very strong oxidising agent. The half-equation which shows its oxidising ability is:

Cr2O7 2− + 14H+ + 6e− → 2Cr 3+ + 7H2O

(i) Use this equation to explain, in terms of oxidation numbers, why the
dichromate ion is an oxidising agent.
[2]
(ii) Use this equation to explain, in terms of electrons, why the dichromate ion is an oxidising agent.
[1]

Answer 4

d)i) Oxidation number in dichromate is +6;
Oxidation number in Cr3+ is +3;
The oxidation number goes down when an oxidant reacts [2]

ii) Oxidising agents gain electrons (which are supplied by the reducing agent) [1]

Question 5

Q13 a) There are several types of structure which apply to chemical formulae. The species present may be atoms, molecules or ions. In each of the following examples describe which type of structure it is and which type of species is present. [6]

Sodium chloride
Diamond
Bromine

Answer 5

Q13 a) Sodium chloride has ions, it has a giant ionic lattice structure [2]
Diamond has atoms, it has a giant covalent structure [2]
Bromine has molecules in it, it has a molecular covalent structure [2]

Question 6

Q13 a) There are several types of structure which apply to chemical formulae. The species present may be atoms, molecules or ions. In each of the following examples describe which type of structure it is and which type of species is present. [6]

Sodium chloride
Diamond
Bromine

b) The different types of structure have different physical properties. State four physical properties that depend upon structure. [3]

Answer 6

Melting point; boiling point; hardness; electrical conductivity

Question 7

Q13 c) The structure of sodium is shown below.

i) Attach words to the labels shown. [2]
ii) Use this diagram to explain whether magnesium has a greater or lower conductivity than sodium. [2]
iii) Explain, using a labelled diagram, how you could compare the electrical conductivities of sodium and magnesium in the laboratory. [3]

Answer 7

c)i) Delocalised electrons [1];
Positive ions; [1]

ii) Magnesium has a greater conductivity [1]; there are more delocalised electrons [1] or magnesium produces 2 delocalised electrons compared to 1 with sodium.

iii) Go look at mark scheme for diagram.
Compare reading on ammeter (brightness of bulb) [1]