DP Chemistry (last assessment 2024)

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Question 18M.2.hl.TZ1.d.iii

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.2.hl.TZ1.d.iii
Level hl Paper 2 Time zone TZ1
Command term Determine Question number d.iii Adapted from N/A
d.iii.
[Maximum mark: 2]
18M.2.hl.TZ1.d.iii

Urea, (H2N)2CO, is excreted by mammals and can be used as a fertilizer.

Urea can also be made by the direct combination of ammonia and carbon dioxide gases.

2NH3(g) + CO2(g) ⇌ (H2N)2CO(g) + H2O(g)     ΔH < 0

Determine an approximate order of magnitude for Kc, using sections 1 and 2 of the data booklet. Assume ΔGΘ for the forward reaction is approximately +50 kJ at 298 K.

[2]

Markscheme

ln K « =  − Δ G Θ R T = − 50 × 10 3  J 8.31  J  K − 1  mo l − 1 × 298  K  » = –20

 

«Kc =» 2 ×  10–9

OR

1.69 ×  10–9

OR

10–9

 

Accept range of 20-20.2 for M1.

Award [2] for correct final answer.

[2 marks]

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