Redox Reactions

The standard ${\mathrm{E}}_{\mathrm{red}}^{°}$ values of A, B  and C are +0.68 V, - 2.54 V,- 0.50 V respectively. The rder of their reducing power is

• A> B >C

• A> C > B

• C > B > A

• B > C > A

Oxidation potential of unimoles of calomel is

• + 0.25 V

• 0.00 V

• + 0.287 V

• -0.28 V

The oxidation number of C atom in CH₂Cl₂ and CCl₄ are respectively

• -2 and -4

• 0 and -4

• 0 and 4

• 2 and 4

The oxidation state of Cr in K₂Cr₂O₇ is

• +4

• +3

• +6

• +5

Potassium dichromate is a good oxidising agent in acidic medium, the oxidation state of chromium changes by

• 2

• 3

• 4

• 5

Which among the following compounds does not act as reducing agent?

• H₂O

• H₂S

• H₂Se

• H₂Te

Which among the following equations represents the reduction reaction taking place in lead accumulator at positive electrode, while it is being used as a source of electrical energy?

• Pb → Pb²⁺

• Pb⁴⁺ → Pb

• Pb²⁺ → Pb

• Pb⁴⁺ → Pb²⁺

When MnO₂ is fused with KOH and KNO₂ , a coloured compound is formed. Choose the right compound with the appropriate colour.

• K₂MnO₄, green

• KMnO₄, purple

• Mn₂O₃, brown

• Mn₃O₄, black

Identify the case(s) where there is change is oxidation number

• Acidified solution of CrO${}_4^{2-}$

• SO₂ gas bubbled through an acidic solution Cr₂O${}_7^{2-}$

• Alkaline solution of CrO${}_7^{2-}$

• Ammoniacal solution of CrO${}_4^{2-}$

In aqueous solution, Cr²⁺ is a stronger reducing agent than Fe²⁺. This is because

• Cr²⁺  ion is more stable than Fe²⁺

• Cr³⁺ ion with d³ configuration has favourable crystal field stabilisation energy

• Cr³⁺ has half filled configuration and hence more stable

• Fe³⁺ in aqueous solution is more stable than Cr³⁺