**Numerical Problems Based on Chemistry Chapter 2 Solutions**

**Q.1**. Calculate the mole fraction of water in a mixture of 12 g water, 108 g acetic acid and 92 ethanol.

Ans. 0.15

**Q.2. **Calculate the mole fraction of ethanol and water in a sample of rectified spirit which contains 95% ethanol by mass.

Ans. Ethanol=0.88, water =0.12

**Q.3. **One litre solution of N/2 HCl is heated in a beaker. It was observed that when the volume of the solution is reduced to 600 mL, 3.25 g of HCl is lost. Calculate the normality of the new solution.

Ans. 0.685 N

**Q.4. **What volume of 95 mass % sulphuric acid (density = 1.85 g/cm^{3}) and what mass of water must be taken to prepare 100 cm^{3} of 15 mass % solution sulphuric acid (density = 1.10 g/cm^{3})?

Ans. 9.4 cm^{3}, 92.6g

**Q.5.** What volume of 10% (w/v) solution of Na_{2}CO_{3} will be required to neutralise 100 mL of HCl solution containing 3.65 g of HCI?

Ans. 53.19 mL

**Q.6. **Concentrated sulphuric acid has a density 1.9 g/mL and is 99% H_{2}SO_{4} by weight calculate molarity of sulphuric acid in the acid.

Ans. 19.19 M

**Q.7. **18 g of glucose (molar mass 180 g mol^{-1}) is present in 500 cm3 of of its aqueous solution. What is the molarity of the solution? What additional data is required if the molality of the solution is also required to be calculated ?

Ans. 0.2M, density of solution is needed to calculate molality of the solution

**Q.8.** Calculate the percentage composition in terms of mass of a solution obtained by mixing 300 g of a 25% and 400 g of a 40% solution by mass.

Ans. 33.57%, 66.43%

**Q.9. **Calculate the molality and mole fraction of the solute in aqueous solution containing 3 g of urea per 250 g of water.

Ans. Molality=0.2 m, Mole fraction = 0.0036

**Q.10. **The molality of a solution of ethyl alcohol (C_{2}H_{5}OH) in water is 1.55 m. How many grams of ethyl alcohol are dissolved in 2 kg of water ?

Ans. 142.6 g

**Q.11.** Commercially available concentrated hydrochloric acid contains 38% HCl by mass and has density 1.19 g cm^{-3}. Calculate the molarity of this solution.

Ans. 12.4 M

**Q.12. **A solution of glucose (C_{6}H_{12}0_{6}) in water is labelled as 10% by weight. What would be the molality of the solution?

Ans. 0.618 m

**Q.13. **Calculate the formality of sodium thiosulphate (Na_{2}S_{2}O_{3}. 5H_{2}0) solution, of which are dissolved in 100 cm of the solution.

Ans. 0.05 F

**Q.14.** 4.0 g of NaOH are contained in one decilitre of a solution. Calculate (i) mole fraction of NaOH (ii) molarity of NaOH (iii) molality of solution. (density of solution = 1.038 g mL^{-1}).

Ans. (i) 0.018 (ii) 1M (iii) 1.002 m

**Q.15. **Calculate the molarity and molality of a solution prepared by mixing equal volumes of 30% by weight of H_{2}SO_{4} density = 1.218 g/mL) and 70% by weight of H_{2}SO_{4} of solution (density = 1.610 g/mL).

Ans. 7.6 M, 11.4 m

**Q.16.** Calculate the molarity of a solution of CaCl_{2} if on chemical analysis it is that 500 mL of CaCl_{2 }solution contain 1.505 x 10^{23} Cl^{–} ions.

Ans. 0.25 M

**Q.17.** The concentration of solution of sulphuric acid is 18 M and has density 1.84 g cm3. What is the mole fraction and weight percentage of H_{2}SO_{4} in the solution?

Ans. 0.81, 95.87%

**Q.18. **Calculate the number of molecules of oxalic acid (H_{2}C_{2}0_{4}. 2H_{2}0) in 100 of 0.2 N oxalic acid solution.

Ans. 6.02 x 10^{21} molecules

**Q.19.** In a solution of benzene in chloroform (CHCl_{3}), the mole fraction of is 0.45. Calculate its percentage by weight in the mixture.

Ans. 34.8%

**Q.20.** 100 mL of a solution containing 5 g of NaOH are mixed with 200 mL of M/5 NaOH solution. Calculate the molarity of the resulting solution.

Ans. 0.55 M

**Q.21.** 8.0575 10^{-2} kg of Glauber’s salt is dissolved in water to obtain 1 dm3 solution of density 1077.2 kg m-3. Calculate (i) the molarity (ii) the molality and (iii) mole fraction of Na_{2}SO_{4}, in the (Atomic masses : Na = 23.00, S = 32.10, 0 = 16.00, H = 1.01)

Ans. (i) 0.25 M (ii) 0.24 M (iii) 0.0043 M

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