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Topic 11: Redo
. x and electrochemistry

16. Redox Reaction: Determining the correct oxidation and reduction equations

1. Given the oxidation-reduction reaction below 2+ 3+
4+
3Sn (aq) + 2Cr(s) ------- 3Sn (aq) + 2Cr (aq)
Which half-reaction correctly shows the oxidation that occurs?
1) Cr (aq) + 3e ------ Cr(s) 3) Cr(s) --------- Cr (aq) + 3e
3+
3+
-
-
4+
2+
2+
-
-
2+
2) Sn (aq) + 2e ------ Sn (aq) 4) Sn (aq) ------- Sn (aq) + 2e

2. In the redox reaction:
3Cu + 2Al -------- 3Cu + 2Al
3+
2+
The oxidation half-reaction is
3+
-
-
2+
1) C u + 2e ------ Cu - 3) Al + 3e ----- Al -
2+
3+
2) Cu ------------------ Cu + 2e 4) Al ------------- Al + 3e
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3. In the redox reaction given below:
2+
2+
0
0
Pb (aq) + Sn (s) -------- Pb (s) + Sn (aq)
Which half-reaction equation is correct for the reduction that occurs? 2+ -
-
2+
0
0
1) Pb (aq) + 2e ------ Pb (s) 3) Sn (s) ------- Sn (aq) + 2e
2+
0
2+
-
0
-
2) Pb (s) + 2e ----- Pb (aq)
4) Sn (aq) ---- Sn (s) + 2e

4. Consider the redox reaction below: 4+ 2-
0
Mn + O2 --------------- > Mn + 2O
Which half-reaction is correct for the reduction that occurs? 0 - 4+
2-
-
1) O2 --------------- 2 O + 4e 3) Mn + 4e ------- Mn -
4+
2-
0
-
4) Mn ------------------ Mn + 4e
2) O2 + 4e ----- 2O

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5. Given the following redox reaction
Mg + 2HBr ------------ MgBr2 + H2
Which equation correctly represents the oxidation that occurs?
1) 2H ----------- H2 + 2e 3) 2H + 2e --------- H2
-
+
+
-
-
0
-
2+
0
2+
2) Mg --------- Mg + 2e 4) Mg + 2e ----------- Mg

6. In the oxidation-reduction reaction
2H2O -------- 2H2 + O2
Which half-reaction equation is correct for the reduction that occurs?
+
2-
-
-
1) 2H + 2e ---------- 2H2 3) 2O + 2e ----- O2
-
2-
-
+
2) 2H2 + 2e ----------- 2H 4) O2 + 2e ----- 2O

7. In the chemical reaction
2AgNO3(aq) + Cu(s) -------- Cu(NO3)2(aq) + 2Ag(s)
Which half-reaction equation correctly shows oxidation? 2+ -
+
-
1) 2Ag (aq) ------------ 2 Ag(s) + 2e 3) Cu(s) ------------ Cu (aq) + 2e
-
-
+
2+
2) 2Ag(s) ------------- 2Ag (aq) + 2e
4) Cu (aq) --------- Cu(s) + 2e

8. Given the following redox chemical reaction
2KClO3 ---------- 2KCl + 3O2
Which half-reaction equation correctly represents the reduction that occurs?
1) 2O ------------------ O2 + 4e 3) Cl ------------------ Cl- + 6e
-
-2
-
5+
-
2-
-
5+
-
2) O2 + 4e --------- 2O 4) Cl + 6e ------- Cl

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