Consider the following redox reaction - HSC - SSCE Chemistry - Question 13 - 2017 - Paper 1
Question 13
Consider the following redox reaction.
2K ext{Cr}_2 ext{O}_7(aq) + 2H_2O(l) + 3S(s) → 2Cr_2O_3(aq) + 4KOH(aq) + 3SO_2(g)
Which species is being oxidised?
A. Cr^6+
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Worked Solution & Example Answer:Consider the following redox reaction - HSC - SSCE Chemistry - Question 13 - 2017 - Paper 1
Step 1
Identify the Oxidation States
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Answer
Begin by determining the oxidation states of the elements involved in the reaction. In ext{K}_2 ext{Cr}_2 ext{O}_7, the oxidation state of chromium (Cr) is +6, while in ext{Cr}_2 ext{O}_3 it is +3. Sulfur (S) starts as 0 in its elemental form and is converted to sulfur dioxide (SO₂) where its oxidation state is +4.
Step 2
Determine the Changes in Oxidation States
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Answer
Next, identify which species undergoes an increase in oxidation state. Chromium decreases from +6 to +3, meaning it is reduced. Sulfur, on the other hand, increases from 0 to +4, indicating it is oxidized.
Step 3
Conclusion
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Answer
From the analysis, the species that is being oxidized is sulfur (S), as it experiences an increase in oxidation state.
