Chemistry Class 11 NCERT Solutions: Chapter 8 Redox Reactions Part 11

Q: 20. What sorts of informations can you draw from the following reaction?

Equation

Answer:

The oxidation number of carbon in Equation and Equation are Equation respectively. These are obtained as shown below:

Let the oxidation number of C be x.

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Equation

The oxidation number of carbon in the various species is:

Equation

It can be easily observed that same compound is being reduced and oxidised simultaneously in the given equation. A reaction in which the same compound is reduced and oxidised is known as disproportionation reactions. Thus, it can be said that the alkaline decomposition of cyanogen is an example of disproportionation reaction.

Q: 21. The Equation ion is unstable in solution and undergoes disproportionation to give Equation Equation , and Equation ion. Write a balanced ionic equation for the reaction.

Answer:

The given reaction can be represented as:

Equation

The oxidation half equation is:

Equation

The oxidation number is balanced by adding one electron as:

Equation

The charge is balanced by adding Equation ions as:

Equation

The O atoms and Equation ions are balanced by adding Equation molecules as:

Equation ……..(i)

The reduction half equation is:

Equation

The oxidation number is balanced by adding one electron as:

Equation ………… (ii)

The balanced chemical equation can be obtained by adding equation (i) and (ii) as:

Equation

Q: 22. Consider the elements:

Cs, Ne, I and F

(A) Identify the element that exhibits only negative oxidation state

(B) Identify the element that exhibits only positive oxidation state

(C) Identify the element that exhibits both positive and negative oxidation state.

(D) Identify the element which exhibits neither the negative nor does the positive oxidation state

Answer:

(A) F exhibits only negative oxidation state of Equation .

(B) Cs exhibits positive oxidation state of Equation .

(C) I exhibits both positive and negative oxidation states. It exhibits oxidation states of

Equation .

(D) The oxidation state of Ne is zero. It exhibits neither negative nor positive oxidation

states.

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