DP Chemistry (last assessment 2024)

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Question 22M.2.hl.TZ1.1b(iii)

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.hl.TZ1.1b(iii)
Level hl Paper 2 Time zone TZ1
Command term Deduce Question number b(iii) Adapted from N/A
b(iii).
[Maximum mark: 2]
22M.2.hl.TZ1.1b(iii)

When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.

The reaction in (a)(i) was carried out in a crucible with a lid and the following data was recorded:

Mass of crucible and lid = 47.372 ±0.001 g

Mass of crucible, lid and magnesium ribbon before heating = 53.726 ±0.001 g

Mass of crucible, lid and product after heating = 56.941 ±0.001 g

 

(b(iii))

Assume the reaction in (a)(i) is the only one occurring and it goes to completion, but some product has been lost from the crucible. Deduce the percentage yield of magnesium oxide in the crucible.

 

[2]

Markscheme

⟨⟨ 0.2614 mol × (24.31 g mol-1+16.00 g mol-1)=0.2614 mol×40.31 g mol-1⟩⟩=10.536 «g» ✔

⟨⟨100×9.569 g10.536 g= 90.822⟩⟩=91 «%» ✔

 

Award «0.2614 mol x 40.31 g mol–1»

Accept alternative methods to arrive at the correct answer.

Accept final answers in the range 90.5-91.5%

[2] for correct final answer.

Examiners report

Satisfactory performance; however, a good number could not answer the question correctly on determining the percentage yield.

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