Question 18M.3.hl.TZ1.5
| Date | May 2018 | Marks available | [Maximum mark: 8] | Reference code | 18M.3.hl.TZ1.5 |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Calculate, Deduce, Determine, Outline | Question number | 5 | Adapted from | N/A |
Aluminium is produced by the electrolysis of a molten electrolyte containing bauxite.
The diagram illustrates the crystal structure of aluminium metal with the unit cell indicated. Outline the significance of the unit cell.
[1]
the smallest repeating unit «from which the crystal structure can be derived»
Accept “building block that the structure is made from”.
[1 mark]
When X-rays of wavelength 0.154 nm are directed at a crystal of aluminium, the first order diffraction pattern is observed at 18°. Determine the separation of layers of aluminium atoms in the crystal, in m, using section 1 of the data booklet.
[2]
«nλ = 2d sin θ»
1 × 1.54 × 10–10 = 2 × d × sin 18
d «» = 2.49 × 10–10 «m»
Award [2] for correct final answer.
[2 marks]
The graph of the resistance of aluminium with temperature is shown below.
Deduce what the shape of the graph indicates about aluminium.
[2]
type 1
superconductor
[2 marks]
Outline why the resistance of aluminium increases above 1.2 K.
[1]
collisions between electrons and «lattice of metal» ions become more frequent
OR
thermal oscillations/vibrations disrupt the Cooper electron pairs
[1 mark]
The concentration of aluminium in drinking water can be reduced by precipitating aluminium hydroxide. Calculate the maximum concentration of aluminium ions in water of pH 7 at 298 K. Solubility product of aluminium hydroxide = 3.3 × 10−34 at 298 K.
[2]
Ksp = [Al3+][OH–]3 «= 3.3 × 10–34»
[Al3] = «» 3.3 × 10–13 «mol dm–3»
Award [2] for correct final answer.
[2 marks]