Chemistry Class 12 NCERT Solutions: Chapter 2 Solutions Part 14

Q: 33. Equation of Equation is dissolved in Equation of water. The depression in the freezing point of water observed is Equation . Calculate the van't Hoff factor and dissociation constant of fluoroacetic acid.

Answer:

It is given that:

Equation

Equation

Equation

Equation

We know that:

Equation

Equation

Equation

Therefore, observed molar mass of Equation

The calculated molar mass of Equation is:

Equation

Equation

Therefore, van’t Hoff factor, Equation

Equation

Equation

Let α be the degree of dissociation of Equation

Equation

Equation

Equation

Equation

Equation

Equation

Now, the value of Equation is given as:

Equation

Equation

Equation

Taking the volume of the solution as Equation , we have the concentration:

Equation

Equation

Therefore, Equation

Equation

Equation

Equation

Equation

Q: 34. Vapour pressure of water at 293 K is 17.535 mm Hg. Calculate the vapour pressure of water at 293 K when 25 g of glucose is dissolved in 450 g of water.

Answer:

Vapour pressure of water, Equation of Hg

Mass of glucose, Equation

Mass of water, Equation

We know that,

Molar mass of glucose Equation

Equation

Molar mass of water, Equation

Then, number of moles of glucose, Equation

Equation

And, number of moles of water, Equation

Equation

We know that,

Equation

Equation

Equation

Equation

Equation

Hence, the vapour pressure of water is Equation of Hg.

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