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Split the following redox reactions into the oxidation and reduction half reactions:
(a) 2K(s) + Cl2(g) ⟶ 2KCl(s)
(b) 2Al(s) + 3Cu2+(aq) ⟶ 2Al3+(aq) + 3Cu(s)
The e.m.f. (E°) of the following cells are:
Ag | Ag+ (1M) || Cu2+ (1M) | Cu; E° = −0.46 V
Zn | Zn2+ (1M) || Cu2+ (1M) | Cu; E° = +1.10 V
Calculate the e.m.f. of the cell:
Zn | Zn2+ (1M) || Ag+ (1M) | Ag
Why blue colour of copper sulphate solution gets discharged when zinc rod is dipped in it?
(Given E°(Cu2+, Cu) = 0.34 V and E°(Zn, Zn2+) = 0.76 V)
Is it safe to stir 1M AgNO3 solution with a copper spoon?
Given:
E°(Ag+,Ag) = 0.80 V
E°(Cu,Cu2+) = −0.34 V
Calculate the oxidation number of
(i) S in H2S
(ii) C in CO2
(iii) C in CH2Cl2
(iv) N is (NH4)2SO4
(v) Pb in Pb3O4
(vi) P in Na3PO4
Predict whether zinc and silver react with 1 M sulphuric acid to give out hydrogen or not.
Given that the standard potentials of zinc and silver are –0.76 volt and +0.80 volt respectively.
Predict reaction of 1N sulphuric acid with the following metals:
(i) Copper
E°(Cu2+/Cu) = +0.34 V
(ii) Lead
E°(Pb2+/Pb) = −0.13 V
(iii) Iron
E°(Fe2+/Fe) = −0.44 V
Balance the following equations in basic medium by both oxidation number and ion electron methods and identify the reductants and the oxidants.
(i) Cu + Au+ ⟶ Au + Cu2+
(ii) Sn(s) + NO3−(aq) + H+(aq) ⟶ Sn2+(aq) + NH4+(aq) + H2O(l)
(iii) Cu(s) + NO3−(aq) + H+(aq) ⟶ Su2+(aq) + NH4+(aq) + H2O(l)
(iv) Zn(s) + NO3−(aq) + H+(aq) ⟶ Zn2+(aq) + N2O(g) + H2O(l)
(v) Sn(aq) + NO3−(aq) + H+(aq) ⟶ SnO32−(aq) + NO2(g) + H2O(l)
(vi) As(s) + NO3−(aq) + H+(aq) ⟶ AsO43−(aq) + NO2(g) + H2O(l)
(vii) Cr2O72−(aq) + Fe2+(aq) ⟶ Cr3+(aq) + Fe3+(aq)
(viii) MnO4−(aq) + Fe2+(aq) ⟶ Mn2+(aq) + Fe3+(aq)
(ix) S + HNO3 ⟶ SO2 + NO2 + H2O
Balance the following redox reactions:
(i) SnO2 + C ⟶ Sn + CO
(ii) Fe3O4 + C ⟶ Fe + CO
(iii) I2 + HNO3 ⟶ HIO3 + NO2 + H2O
(iv) FeSO4 + HNO3 + H2SO4 ⟶ Fe2(SO4)3 + NO + H2O
(v) Fe + HNO3 ⟶ Fe(NO3)2 + NH4NO3 + H2O
(vi) Sb + HNO3 ⟶ H3SbO4 + NO2 + H2O
(vii) Hg + HNO3 ⟶ Hg2(NO3)2 + NO + H2O
What is the oxidation number of metals in:
(i) [Fe(CN)6]4−
(ii) MnO4−
Using electron-transfer concept, identify the oxidant and reductant in the following redox reactions:
(a) Zn(s) + 2H+(aq) ⟶ Zn2+(aq) + H2(g)
(b) 2[Fe(CN)6]4−(aq) + H2O2(aq) + 2H+(aq) ⟶ 2[Fe(CN)6]3−(aq) + 2H2O(l)
(c) 2[Fe(CN)6]3−(aq) + 2OH−(aq) + H2O2(aq) ⟶ 2[Fe(CN)6]4−(aq) + O2(g) + 2H2O(l)
(d) BrO3−(aq) + F2(g) + 2OH−(aq) ⟶ BrO4−(aq) + 2F−(aq) + H2O(l)
(e) 2NaClO3(aq) + I2(aq) ⟶ 2NaIO3(aq) + Cl2(g)
In the reactions given below, identify the species undergoing oxidation and reduction:
(i) CH4(g) + 2O2(g) ⟶ CO2(g) + 2H2O(l)
(ii) 2H2S(g) + O2(g) ⟶ 2S(s) + 2H2O(l)
(iii) CH2 = CH2(g) + H2(g) ⟶ H3C — CH3(g)
(iv) 2HgO(s) ⟶(Δ) 2Hg(l) + O2(g)
(v) Mg(s) + S(s) ⟶ MgS(s)
Write the cell reaction and calculate the standard E° of the cell:
Zn | Zn2+ (1M) || Cd2+ (1M) | Cd
Given:
E°(Zn/Zn2+) = 0.763 V
E°(Cd/Cd2+) = 0.403 V
Identify the oxidant and reductant in the following reactions:
(a) 10H+(aq) + 4Zn(s) + NO3−(aq) ⟶ 4Zn2+(aq) + NH4+(aq) + 3H2O(l)
(b) I2(g) + H2S(g) ⟶ 2HI(g) + S(s)
Can a solution of 1M ZnSO4 be stored in a vessel made of copper?
Given:
E°(Zn2+/Zn) = +0.76 V
E°(Cu2+/Cu) = +0.34 V
Balance the following equations in acidic medium by both oxidation number and ion electron methods and identify the oxidants and the reductants:
Equations:
(i) MnO4 −(aq) + C2H2O4(aq) ⟶ Mn2+(aq) + CO2(g) + H2O(l)
(ii) H2S(aq) + Cl2(g) ⟶ S(s) + Cl−(aq)
(iii) MnO4 −(aq) + C2H5OH(aq) ⟶ Mn2+(aq) + CO2COOH(aq)
(iv) Bi(s) + NO3 −(aq) ⟶ Bi3+(aq) + NO2(g)
(v) Cr2O7 2−(aq) + C2H4O(aq) ⟶ Cr3+(aq) + C2H4O2(aq)
(vi) MnO4 −(aq) + Br−(aq) ⟶ Mn2+(aq) + Br2(aq)
(vii) Cu(aq) + NO3 −(aq) ⟶ Cu2+(aq) + NO2(g)
(viii) H2S(g) + Fe3+(aq) ⟶ Fe2+(aq) + S(s) + H+(aq)
(ix) I−(aq) + IO3 −(aq) + H+(aq) ⟶ I2(aq) + H2O(l)
(x) I−(aq) + O2(g) + H2O(l) ⟶ I2(aq) + OH−(aq)
Two half cells are Al3+(aq)/Al and Mg2+(aq)/Mg
The reduction potentials of these half cells are:
Al3+/Al = −1.66 V
Mg2+/Mg = −1.36 V
Calculate the cell potential. Write the cell reactions also.
Write the half reactions for the following redox reactions:
(a) 2Fe3+(aq) + 2I−(aq) ⟶ 2Fe2+(aq) + I2(aq)
(b) Zn(s) + 2H+(aq) ⟶ Zn2+(aq) + H2(g)
(c) Al(s) + 3Ag+(aq) ⟶ Al3+(aq) + 3Ag(s)