DP Chemistry (last assessment 2024)

Question 20N.3.hl.TZ0.c(ii)

Date	November 2020	Marks available	[Maximum mark: 3]	Reference code	20N.3.hl.TZ0.c(ii)
Level	hl	Paper	3	Time zone	TZ0
Command term	Calculate	Question number	c(ii)	Adapted from	N/A

c(ii).

[Maximum mark: 3]

20N.3.hl.TZ0.c(ii)

There has been significant growth in the use of carbon nanotubes, CNT.

Pure magnesium needed for making alloys can be obtained by electrolysis of molten magnesium chloride.

Calculate the theoretical mass of magnesium obtained if a current of 3.00 A is used for $10.0$ hours. Use charge :(Q) = current (I) × time (t) and section 2 of the data booklet.

[3]

Markscheme

$« Q = I \times t = 3.00 \times 10.0 \times 3600 = » 108 000 C$ ✔

$« \frac{Q}{F} = \frac{108 000 C}{96 500 C {mol}^{- 1}} = » 1.12 « mol e^{-} »$ ✔

$« \frac{1.12 mol}{2} = 0.560 mol Mg »$
$« m = 0.560 mol \times 24.31 g {mol}^{- 1} = » 13.6 « g »$ ✔

Award [3] for correct final answer.

Examiners report

The better candidates scored all three marks for the electrolysis calculation. Even the weaker candidates managed to score at least one mark for calculating Q = 108,000 C.

Syllabus sections

Options

Options » A: Materials » A.2 Metals and inductively coupled plasma (ICP) spectroscopy

Options » A: Materials

Question 20N.3.hl.TZ0.c(ii)

Select a Test

Syllabus sections

Confirm action