Redox Reactions

On balancing the given redox reaction, a Cr2O72-(aq) + b SO32-(aq) + cH+(aq) 2a Cr3+(aq) + b SO42-(aq) + c2H2O( ) the coefficients a, b and c are found to be, respectively -

1. 3, 8, 1
2. 1, 8, 3
3. 8, 1, 3
4. 1, 3, 8

Which of the following reactions is a decomposition redox reaction?

1. P4(s) + 3OH-(aq) + 3H2O(l) PH3(g) + 3H2PO2-(aq)
2. 2Pb(NO3)2(s) 2PbO(s) + 4NO2(g) + O2(g)
3. N2(g) + O2(g) 2NO(g)
4. Cl2(g) + 2OH-(aq) ClO-(aq) + Cl-(aq) + H2O(l)

Which of the following reactions is the metal displacement reaction? Choose the right option.

1. 2Pb(NO3)2 2PbO + 4NO2 + O2
2. 2KClO3 2KCl + 3O2
3. Cr2O3 + 2Al Al2O3 + 2Cr
4. Fe + 2HCl FeCl2 + H2

What is the change in oxidation number of carbon in the following reaction? CH4(g) + 4Cl2(g) CCl4(l) + 4HCl(g)

1. 0 to +4
2. -4 to +4
3. 0 to -4
4. +4 to +4

Which of the following reactions are disproportionation reaction? Select the correct option from the following :

1. A, C and D
2. A and B only
3. A and D only
4. A, B and C

Consider the change in oxidation state of bromine corresponding to different emf values as shown in the given diagram : BrO4- 1.82 V BrO3- 1.5 V HBrO 1.595 V Br2 1.0652 V Br- Then the species undergoing disproportionation is :

1. BrO4-
2. BrO3-
3. Br2
4. HBrO

The correct order of N-compounds in its decreasing order of oxidation states is

1. HNO3, NO, N2, NH4Cl
2. HNO3, NO, NH4Cl, N2
3. HNO3, NH4Cl, NO, N2
4. NH4Cl, N2, NO, HNO3

For the redox reaction, MnO4- + C2O42- + H+ Mn2+ + CO2 + H2O The correct coefficients of the reactants for the balanced equation are

1. array|c|c|c| MnO4- & C2O42- & H+ \ 16 & 5 & 2 \ array
2. array|c|c|c| MnO4- & C2O42- & H+ \ 2 & 5 & 16 \ array
3. array|c|c|c| MnO4- & C2O42- & H+ \ 2 & 16 & 5 \ array
4. array|c|c|c| MnO4- & C2O42- & H+ \ 5 & 16 & 2 \ array

Assuming complete ionisation, same moles of which of the following compounds will require the least amount of acidified KMnO4 for complete oxidation?

1. FeSO3
2. FeC2O4
3. Fe(NO2)2
4. FeSO4

Which of the following processes does not involve oxidation of iron?

1. Formation of Fe(CO)5 from Fe.
2. Liberation of H2 from steam by iron at high temperature.
3. Rusting of iron sheets.
4. Decolourisation of blue CuSO4 solution by iron.