Chemistry Class 11 NCERT Solutions: Chapter 8 Redox Reactions Part 12

Q: 23. Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

Answer

The given redox reaction can be represented as:

Equation

The oxidation half reaction is:

Equation

The oxidation number is balanced by adding two electrons as:

Equation

The charge is balanced by adding Equation ions as:

Equation ……… (i)

The reduction half reaction is:

Equation

The chlorine atoms are balanced as:

Equation

The oxidation number is balanced by adding electrons

Equation …………..(ii)

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

Equation + Equation

Q: 24. Refer to the periodic table given in your book and now answer the following questions:

(a) Select the possible nonmetals that can show disproportionation reaction.

(b) Select three metals that can show disproportionation reaction.

Answer:

In disproportionation reactions, one of the reacting substances always contains an element that can exist in at least three oxidation states.

(A) P, Cl, and S can show disproportionation reactions as these elements can exist in three or more oxidation states.

(B)Mn, Cu, and Ga can show disproportionation reactions as these elements can exist in three or more oxidation states.

Q: 25. In Ostwald’s process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.00 g. of ammonia and 20.00 g of oxygen?

Answer

The balanced chemical equation for the given reaction is given as:

Equation

Thus, 68 g of NH3 reacts with 160 g of O2.

Therefore, 10g of NH3 reacts with Equation g of Equation .

But the available amount of Equation .

Therefore, Equation is the limiting reagent (we have considered the amount of Equation to calculate the weight of nitric oxide obtained in the reaction).

Now, 160 g of Equation gives 120g of NO.

Therefore, 20 g of Equation gives Equation g of N, or Equation of Equation .

Hence, a maximum of 15 g of nitric oxide can be obtained.

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