Redox reactions
Answers are for parents and teachers.
1
For S + O₂ → SO₂ write the changes of oxidation states and name the oxidizing agent.
S: 0 → +4 (reducing agent); O: 0 → –2 (oxidizing agent O₂).
2
Balance H₂S + Cl₂ → HCl + S by electron balance.
H₂S + Cl₂ → 2HCl + S
3
In Fe₂O₃ + 3CO → 2Fe + 3CO₂ each of the two Fe³⁺ ions takes 3 electrons. How many electrons pass in total?
6
4
In Cu + 4HNO₃(conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O how do the states of Cu and N change? (paper only; this reaction gives a toxic gas.)
Cu: 0 → +2; N: +5 → +4.
5
Why is CaCO₃ → CaO + CO₂ not a redox reaction?
No element changes its oxidation state (Ca +2, C +4, O –2).