Chromium is a transition metal with many industrial applications. Most chromium is found as oxides or as part of complex minerals such as chromite, FeCr2O4\text{FeCr}_2\text{O}_4FeCr2O4.
Complete the table by giving the names of the elements represented by the chemical symbols in FeCr2O4\text{FeCr}_2\text{O}_4FeCr2O4:
| Chemical symbol | Name of element |
|---|---|
| Fe | |
| Cr | |
| O |
In one extraction process, chromium(III) oxide, Cr2O3\text{Cr}_2\text{O}_3Cr2O3, is reduced using magnesium to produce chromium metal according to the word equation:
chromium(III) oxide+magnesium→chromium+magnesium oxide \text{chromium(III) oxide} + \text{magnesium} \rightarrow \text{chromium} + \text{magnesium oxide} chromium(III) oxide+magnesium→chromium+magnesium oxideWrite a balanced chemical equation for this reaction.
Explain what the reaction shows about the reactivity of chromium compared to the reactivity of magnesium.
Explain why the reaction between chromium(III) oxide and magnesium is described as a redox reaction.
Chromium metal reacts with dilute hydrochloric acid to form hydrogen gas.
This apparatus is used to investigate the reaction:
The equation for the reaction is:
Cr(s)+2HCl(aq)→CrCl2(aq)+H2(g) \text{Cr}(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CrCl}_2\text{(aq)} + \text{H}_2\text{(g)} Cr(s)+2HCl(aq)→CrCl2(aq)+H2(g)A student adds 0.39 g0.39\text{ g}0.39 g of a sample of chromium metal to excess dilute hydrochloric acid.
Calculate the maximum volume, in dm3\text{dm}^3dm3, of hydrogen gas that the student could produce in this experiment at room temperature and pressure (rtp).
[Relative atomic mass: Ar(Cr)=52A_r(\text{Cr}) = 52Ar(Cr)=52; molar volume of a gas is 24 dm324\text{ dm}^324 dm3 at rtp]
The student does the experiment at rtp and finds that the volume collected is less than the calculated maximum. Give two possible reasons for this.
