DP Chemistry (last assessment 2024)

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Question 19M.2.hl.TZ2.d(i)

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.hl.TZ2.d(i)
Level hl Paper 2 Time zone TZ2
Command term Suggest Question number d(i) Adapted from N/A
d(i).
[Maximum mark: 2]
19M.2.hl.TZ2.d(i)

Ethyne, C2H2, reacts with oxygen in welding torches.

Product B, CH3CHO, can also be synthesized from ethanol.

Suggest the reagents and conditions required to ensure a good yield of product B.

Reagents: 

Conditions:

[2]

Markscheme

Reagents:
acidified/H+ AND «potassium» dichromate«(VI)»/K2Cr2O7/Cr2O72-    [✔]

Conditions:
distil «the product before further oxidation»       [✔]

 

Note: Accept “«acidified potassium» manganate(VII)/KMnO4/MnO4-/permanganate”.

Accept “H2SO4” or “H3PO4” for “H+”.

Accept “more dilute dichromate(VI)/manganate(VII)” or “excess ethanol”.

Award M1 if correct reagents given under “Conditions”.

Examiners report

Candidates seemed to be confused by the prompts, reagent and conditions, so often included the acid among conditions. Careless errors were common such as the wrong charge on the dichromate ion. Few candidates suggest permanganate as an option.

Syllabus sections