Sodium chromate(VI), $$$\mathrm{Na}_{2} \mathrm{CrO}_{4}$$$, is manufactured by heating chromite, $$$\mathrm{FeCr}_{2} \mathrm{O}_{4}$$$, with sodium carbonate in an oxidising atmosphere. Chromite contains $$$\mathrm{Cr}_{2} \mathrm{O}_{4}{ }^{2-}$$$ ions. $$\[ 2 \mathrm{FeCr}_{2} \mathrm{O}_{4}+4 \mathrm{Na}_{2} \mathrm{CO}_{3}+3 \frac{1}{2} \mathrm{O}_{2} \rightarrow 4 \mathrm{Na}_{2} \mathrm{CrO}_{4}+\mathrm{Fe}_{2} \mathrm{O}_{3}+4 \mathrm{CO}_{2} \]$$ What happens in this reaction?

Chromium and iron are the only elements oxidised.

Chromium, iron and carbon are oxidised.

Only chromium is oxidised.

Only iron is oxidised.

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_11 Year：2024 Question No：11

Answer:

6.1.1 calculate oxidation numbers of elements in compounds and ions

6.1.2 use changes in oxidation numbers to help balance chemical equations

6.1.3 explain and use the terms redox, oxidation, reduction and disproportionation in terms of electron transfer and changes in oxidation number

6.1.4 explain and use the terms oxidising agent and reducing agent

6.1.5 use a Roman numeral to indicate the magnitude of the oxidation number of an element