Question 1

What is the stoichiometric coefficient of SO _2 in the following balance reaction? MnO _4^ - (a q)+ SO _2(g) Mn ^ 2+ (a q)+ HSO _4^ - (a q) (in acidic solution)

Accepted Answer

Oxidation half reaction: SO _2( ~g )+2 H _2 O (l) HSO _4^ - (a q)+3 H ^ + (a q)+2 e^ - ...(i) Reduction half reaction: MnO _4^ - (a q)+8 H ^ + +5 e^ - Mn ^ 2+ (a q)+4 H _2 O (l)...(ii) Multiply eq. (i) by 5 and (ii) by 2 and then add aligned 2 MnO _4^ - (a q)+5 SO _2(g) & +2 H _2 O (l)+ H ^ + (a q) \ & 2 Mn ^ + (a q)+5 HSO _4^ - (a q) aligned Thus, the stoichiometric coefficient of SO _2 in the above balance equation is 5 .

Question 2

Volume of M / 8 KMnO _4 solution required to react completely with 25.0 ~cm ^3 of M / 4 FeSO _4 in acidic medium is.

Accepted Answer

The balance ionic equation for the reaction is MnO _4^ - +5 Fe ^ 2+ +8 H ^ + Mn ^ 2+ +5 Fe ^ 3+ +4 H _2 O From the above equation it is clear that 1 mole of KMnO _4=5 moles of FeSO _4. Apply molarity equation to balance the redox reaction aligned M_1 V_1 n_1 ( KMnO _4 ) & = M_2 V_2 n_2 ( FeSO _4 ) \ 1 V_1 8 1 & = 1 4 25 5 \ V_1 & = 1 25 8 4 5 \ V_1 & =10 ~cm ^3 or V_1=10.0 ~mL aligned

Question 3

Which of the following is only a redox reaction but not a disproportionation reaction?

Accepted Answer

The reaction P _4+8 SOCl _2 4 PCl _3+2 ~S _2 Cl _2 +4 SO _2 involves change of oxidation state of P from 0 to +3 and that of S from +4 to +2 . Thus, it is a redox reaction but not a disproportionation reaction.

Question 4

For the reaction: NH _ 3 + OCl ^ - N _ 2 H _ 4 + Cl ^ - in basic medium, the coefficients of NH _ 3 , OCl ^ - and N _ 2 H _ 4 for the balanced equation are respectively

Accepted Answer

The balanced equation : 2 NH _ 3 + OCl ^ - N _ 2 H _ 4 + Cl ^ - + H _ 2 O

Question 5

Which of the following is not a disproportionation reaction?

Accepted Answer

Disproportionation involves simultaneous oxidation and reduction of the same atom in a molecule.

Redox Reactions — Previous Year Questions & Solutions