Chromium is a transition metal that can be extracted from its chief ore, chromite, in a multi-stage process.
A sample of chromite ore has the following composition by mass:
Fe=24.9%,Cr=46.5%,O=28.6% \text{Fe} = 24.9\%, \quad \text{Cr} = 46.5\%, \quad \text{O} = 28.6\% Fe=24.9%,Cr=46.5%,O=28.6%Show by calculation that the empirical formula of this ore is FeCr2O4\text{FeCr}_2\text{O}_4FeCr2O4. [Relative atomic masses, ArA_rAr: O=16.0\text{O} = 16.0O=16.0, Cr=52.0\text{Cr} = 52.0Cr=52.0, Fe=55.8\text{Fe} = 55.8Fe=55.8]
In one extraction method, chromium(III) oxide (Cr2O3\text{Cr}_2\text{O}_3Cr2O3) is reacted with aluminium at high temperatures:
Cr2O3+2Al→2Cr+Al2O3 \text{Cr}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Cr} + \text{Al}_2\text{O}_3 Cr2O3+2Al→2Cr+Al2O3Explain which element has been oxidised in this reaction.
Describe the bonding in chromium metal.
Explain why chromium metal conducts electricity.
80 exam-style questions on Edexcel IGCSE Chemistry Chemical formulae, equations and calculations. Each one has a worked solution and a mark scheme showing where the marks go.