# Chemistry Class 12 NCERT Solutions: Chapter 2 Solutions Part 1

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Q: 1. Calculate the mass percentage of benzene and carbon tetrachloride dissolved in of carbon tetrachloride.

Ans:

Mass percentage of

Alternatively,

Mass percentage of

Q: 2. Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.

Ans:

Let the total mass of the solution be and the mass of benzene be .

∴ Mass of carbon tetrachloride

Molar mass of benzene

∴ Number of moles of

Molar mass of carbon tetrachloride

∴ Number of moles of

Thus, the mole fraction of is given as:

Q: 3. Calculate the molarity of each of the following solutions:

(A) of solution

(B) Diluted to

Ans:

Molarity is given by:

(A) Molar mass of

Therefore, molarity

(B) Number of moles present in 1000 ml of 0.5 M

Therefore, molarity

Q: 4. Calculate the mass of urea required in making molal aqueous solution.

Ans:

Molar mass of urea

Molar aqueous solution of urea means:

of water contains of urea

of urea

That is,

of solution contains of urea

Therefore, of solution contains

(Approximately)

Hence, mass of urea required

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