Chemistry Class 11 NCERT Solutions: Chapter 7 Equilibrium Part 28

Chemistry Class 11 NCERT Solutions Chapter 7 Equilibrium Part 28

Q: 71. What is the maximum concentration of equimolar solutions of ferrous sulphate and sodium sulphide so that when mixed in equal volumes, there is no precipitation of iron sulphide? (For iron sulphide, Equation .

Answer:

Let the maximum concentration of each solution be x mol/L. After mixing, the volume of the concentrations of each solution will be reduced to half i.e., Equation .

Equation Equation

Then, Equation

Also, Equation

Equation

Equation

Equation

Equation

Equation M

If the concentrations of both solutions are equal to or less than Equation M, then there will be no precipitation of iron sulphide.

Q: 72. What is the minimum volume of water required to dissolve 1g of calcium sulphate at 298 K? (For calcium sulphate, Equation ).

Water dissolving another compound

Structure of H2O

Water dissolving another compound

Answer:

Equation

Equation

Let the solubility of Equation be S.

The, Equation

Equation

Equation

Molecular mass of Equation

Solubility of Equation in gram/L Equation

Equation

This means that we need 1L of water to dissolve Equation

Therefore, to dissolve 1g of Equation we require Equation of water

Q: 73. The concentration of sulphide ion in 0.1M HCl solution saturated with hydrogen sulphide is Equation M. If 10 mL of this is added to 5 mL of 0.04 M solution of the following: Equation . in which of these solutions precipitation will take place? Give Equation

Equation

Structure of Hydrogen Sulphide

Structure of Hydrogen Sulphide

Structure of Hydrogen Sulphide

Answer: For precipitation to take place, it is required that the calculated ionic product exceeds the Equation value.

Before mixing:

Equation

Equation

Equation

Ionic Product Equation

Equation

Equation

This ionic product exceeds the Equation of Equation and CdS. Therefore, precipitation will occur in

CdCl2 and ZnCl2 solutions.

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