The material covered in this homework applies to processes occurring at the Eart
ID: 517842 • Letter: T
Question
The material covered in this homework applies to processes occurring at the Earth's surface. Show all your work. Balance the following oxidation reduction reactions (from Faure). i. MnO_4^- Cl^- leftrightarrow Mn^2+ + Cl_2 ii. As_2S_3 + NO_3^- leftrightarrow HASO_3 + S + NO iii. Cr_2O_7^2- + I^- leftrightarrow Cr^3+ + I_2 iv. CrO_2^- + ClO^- leftrightarrow CrO_4^2- + Cl^- v. CH_4^0 + SO_4^2- leftrightarrow HCO_3^- + HS^- Balance the following four overall redox reactions. Which reactions will generate acid and why is this a problem? i. Cu_5FeS_4 (bornite) + O_2 (g) leftrightarrow Cu^2+ + Fe(OH)_3 (s) + SO_4^2- ii. ZnS + O_2 (g) leftrightarrow Zn^2+ + SO_4^2- iii. Fe_3S_4 + O_2 (g) leftrightarrow Fe(OH)_3 (s) + SO_4^2- iv. FeS_2 Pyrite + NO_3^- leftrightarrow N_2 (g) + FeOOH_Goethite + SO_4^2-Explanation / Answer
(i)
MnO4- + Cl- ---------> Mn2+ + Cl2
Seperate oxidation and reduction half reactions
(a)
Cl- ----------> Cl2 oxidation half reaction
MnO4- ---------> Mn2+ Reduction Half Reaction
(b) Balance atoms other than O and H
2 Cl- ----------> Cl2
MnO4- ---------> Mn2+
(c)
To balance oxygen atoms in acidic medium add H2O molecules.
2 Cl- ----------> Cl2
MnO4- ---------> Mn2+ + 4 H2O
(d) To balance hydrogen atoms in acidic medium add H+ ions.
2 Cl- ----------> Cl2
MnO4- + 8 H+---------> Mn2+ + 4 H2O
(e) To balance charges add electrons
2 Cl- ----------> Cl2 + 2 e
MnO4- + 8 H++ 5 e ---------> Mn2+ + 4 H2O
(f) To equalise electrons in both half reactions multiply with suitabel numbers.
10 Cl- ----------> 5 Cl2 + 10 e
2 MnO4- + 16 H++ 10 e ---------> 2 Mn2+ + 8 H2O
(g) Add both half reactions to get balanced equation.
2 MnO4- + 16 H++ 10 Cl- ----------> 5 Cl2 + 2 Mn2+ + 8 H2O
this is the balanced equation.
follow the similar procedure for remaining
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