The oxidation state of Cr in K2Cr2O7 is from Chemistry Redox Rea

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 Multiple Choice QuestionsMultiple Choice Questions

11.

The standard Ered° 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


12.

Oxidation potential of unimoles of calomel is

  • + 0.25 V

  • 0.00 V

  • + 0.287 V

  • -0.28 V


13.

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

  • -2 and -4

  • 0 and -4

  • 0 and 4

  • 2 and 4


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14.

The oxidation state of Cr in K2Cr2O7 is

  • +4

  • +3

  • +6

  • +5


C.

+6

Let the oxidation state of Cr be x

2(+1) + 2x + 7(-2) = 0

          +2 + 2x - 14 = 0

                   2x - 12 = 0

                            x = +6

Therefore, the oxidation number of Cr in K2Cr2O7 is +6.


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15.

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

  • 2

  • 3

  • 4

  • 5


16.

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

  • H2O

  • H2S

  • H2Se

  • H2Te


17.

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+


18.

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


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19.

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

  • Acidified solution of CrO42-

  • SO2 gas bubbled through an acidic solution Cr2O72-

  • Alkaline solution of CrO72-

  • Ammoniacal solution of CrO42-


20.

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+


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