What this tests
Syllabus point 3.2 — Relative masses of atoms and molecules, in Stoichiometry. Difficulty hard (estimated from the question's demands, not a Cambridge rating).
Also set in
The same question, as Cambridge printed it in other papers.
Cambridge IGCSE Chemistry 0620 · 3.2 Relative masses of atoms and molecules
November 2020 · Paper 23 · Question 11
One real Cambridge question from Stoichiometry, with the official answer. Cambridge has printed this question 4 times.