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One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol - HSC - SSCE Chemistry - Question 9 - 2009 - Paper 1
Question 9
One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol. In this reaction the orange dichromate ion, Cr2O7^{2-... show full transcript
Worked Solution & Example Answer:One test used for random breath testing in NSW involved crystals of potassium dichromate reacting with ethanol - HSC - SSCE Chemistry - Question 9 - 2009 - Paper 1
Step 1
Which statement is true for this reaction?
Answer
The reaction involves the conversion of dichromate ions (Cr2O7^{2-}) to chromium ions (Cr^{3+}). In this process, chromium is reduced, which means it gains electrons.
To break it down:
- The oxidation state of chromium in Cr2O7^{2-} is +6.
- The oxidation state of chromium in Cr^{3+} is +3.
Since chromium moves from a higher oxidation state (+6) to a lower oxidation state (+3), we conclude that it has gained electrons throughout this reaction. Therefore, the correct statement is:
(C) Chromium has gained electrons and reached a lower oxidation state.