DP Chemistry (last assessment 2024)

Question 21M.2.sl.TZ2.a

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.sl.TZ2.a
Level	sl	Paper	2	Time zone	TZ2
Command term	Calculate	Question number	a	Adapted from	N/A

[Maximum mark: 2]

21M.2.sl.TZ2.a

Limestone can be converted into a variety of useful commercial products through the lime cycle. Limestone contains high percentages of calcium carbonate, CaCO₃.

Calcium carbonate is heated to produce calcium oxide, CaO.

CaCO₃(s) → CaO (s) + CO₂(g)

Calculate the volume of carbon dioxide produced at STP when 555 g of calcium carbonate decomposes. Use sections 2 and 6 of the data booklet.

[2]

Markscheme

«n_CaCO3 = $\frac{555 g}{11.09 g {mol}^{- 1}}$ =» 5.55 «mol» ✓

«V = 5.55 mol × 22.7 dm³ mol⁻¹ =» 126 «dm³» ✓

Award [2] for correct final answer.

Accept method using pV = nRT to obtain the volume with p as either 100 kPa (126 dm³) or 101.3 kPa (125 dm³).

Do not penalize use of 22.4 dm³ mol^–1 to obtain the volume (124 dm³).

Syllabus sections

Core

Core » Topic 1: Stoichiometric relationships » 1.3 Reacting masses and volumes

Core » Topic 1: Stoichiometric relationships

Question 21M.2.sl.TZ2.a

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