CBSE Guess > Papers > Important Questions > Class XII > 2007 > Chemistry > Numericals

Numericals

Q. 1. How many millimoles of N₂ gas would dissolve in 1 litre of water at 293 K? N₂ exerts a partial pressure of 0.987 bar. (Henry's Law constant at 293 K for N₂ is 76.4 K bar)

Q. 2. Na₂CO₃ and NaHCO₃ mixture containing Ig is neutralised by 0.1M HCI. Find the volume of HCI equired if the mixture contains equimolar amounts of Na₂CO₃ and NaHCO₃.

Q. 3. Calculate the percentage composition in terms of mass of a solution obtained by mixing 300g of 25% and 400g of 40% solution by mass.

Q. 4. A sample of drinking water contains 15 ppm of CHCI₃ (by mass). Express this in percentage by mass. Determine the molality of CHCI₃ in solution.

Q. 5. The partial pressure of ethane over a saturated solution containing 6.56 x 10^-2 g of ethane is 1 bar. If the solution containing 5.00 x 10^-2 g, then what will be the partial pressure of the gas.

Q. 6. An aqueous solution @2% non-volatile solute exerts a pressure of 1.004 bar at the boiling point of the solvent. Find the molar mass of the solute.

Q. 7. Heptane and octane form an ideal solution at 373K. Vapour pressure of heptane and octane are 105.2 kPa and 46.8 kPa respectively. Find the vapour pressure in bar of a mixture of 25g heptane and 35g octane.

Q. 8. Vapour pressure of water is 12.3 kPa at 300K. Calculate the vapour pressure of 1 molal solute in it.

Q. 9. Two elements A and B form compounds AB₂ and AB₄. When dissolved in 20g benzene, Ig of AB₂ lowers the freezing point by 2.3K, Whereas Ig AB₄ lowers the freezing point by 1.3K. K_f for benzene = 5.1 K kg mole^-1. Calculate the atomic mass of A and B.

Q. 10. At 300K, 36g glucose (molar mass 180) in 1 litre solution exerted an osmotic pressure of 4.98 bar. What would be the concentration of the solution at 300K if the osmotic pressure is 1.52 bar.

Q. 11. Concentrated HN03 is 63% by mass. Density of the solution is 1.5g/cm³. Calculate the volume of the solution which contains 20g HNO₃ (Molar mass HNO₃ = 63).

Q. 12. Concentrated H₂SO₄ is 49% by mass. Density of the solution is 1.5g/cm³. Determine molarity, olality and normality of the solution. (Molar mass of H₂SO₄ = 98)

Q. 13. Calculate the molality of 1M solution of NaNO3. Density is 1.25 g/cm3. (Molar mass of NaNO3 = 85)

Q. 14. Calculate the number of moles of CH₃OH in 5 litres of 2 molal solution. Density is 0.981 g/cm³. Molar mass of CH₃OH = 32)

Q. 15. Calculate the volume of 80% H₂SO₄ (D =1.8 g/cm³) required to prepare 1 litre of 20% H₂SO₄ (D =1.25 g/cm³)

Q. 16. 1.8 grams glucose (Molar mass = 180) is dissolved in 36g of water. Calculate the molality and the mole fraction of glucose in the solution.

Q. 17. Sea water contains 5.8 x 10^-3g dissolved O₂ per kilogram. Express the concentration in ppm.

Q. 18. Calculate the resulting molarity of the solution prepared by adding 5g NaOH to 200ml M/4 NaOH solution. (D = 1.05g/cm³). Density of the resulting solution is 1.08 g/cm³.

Q. 19. Benzene and toluene forms an ideal solution at 300K. p^o benzene = 160mm Hg. p^otoluene = 60mm Hg. Calculate the partial pressure of benzene and toluene and the total pressure under the following conditions:-

1. Mixing equal number of moles of benzene and toluene
2. Equal masses of benzene and toluene
3. Equal amount of benzene and toluene

Q. 20. A solution containing 1 mole of X and 3 moles of Y gave a vapour pressure of 550mm Hg. The same solution containing 1 mole of X and 4 moles of Y gave a vapour pressure of 560mm Hg. Find the vapour pressure of pure X and pure Y.

Q. 21. Vapour pressure of a solution containing benzene and toluene is 180x + 120 at 200K where x is the mole fraction of toluene. Find vapour pressure of pure benzene and pure toluene.

Q. 22. Vapour pressure of aqueous dilute solution of glucose is 750mm Hg at 373K. Find the molality and mole fraction of glucose in the solution.

Q. 23. Vapour pressure of ethanol (Molecular mass = 46) and methanol (Molecular mass = 32) at 300K are 45mm Hg and 90mm Hg respectively. Find the total pressure of the solution containing 92g ethanol and 16g methanol.

Q. 24. (a) Vapour pressure of pure benzene (Molecular mass = 78) at 300K is 640mm Hg. 2.175g of non-volatile solute in 39g benzene gave a vapour pressure of 600mm Hg. Determine the molar mass of the solute.

(b). 5% Solution of Sucrose(Molarmass=342)is isotonic with 0.877%Solution of urea.Find the molar mass of urea

Q. 25. A very small amount of solute in 60cm³ benzene showed a vapour pressure of 98.88mm Hg. Vapour pressure of pure benzene is 100mm Hg at this temperature. Find the molality of the solution. If AT_f = 0.73K find K_fof benzene.

Q. 26. A solution of sucrose (Molecular mass = 342) is prepared by dissolving 68.4g in lOOg H₂0. Determine

1. Vapour pressure of solution at 298K.
2. Osmatic pressure at 298K.
3. Boiling point of the solution
4. Freezing point of the solution
   Given Kb = 0.52 K Kg mole^-1, Kf = 1.86 K Kg mole^-1 , R = 0.0821 I atm K-mole^-1

Q. 27. 34.2g sucrose and 36g glucose are dissolved in 81g H₂0. Find the vapour pressure of the solution. Vapour pressure of H₂O = 30mm Hg. Molecular mass of sucrose = 342, Glucose = 180.

Q. 28. Calculate the boiling point and freezing point of 1M solution of KCI. D = 1.04 g/cm³. Molar mass of KCI = 74.5. K_b = 0.52 K Kg mole-1 K_f = 1.86 K Kg mole^-1. Assume KCI is 90% dissociated.

Q. 29. BaCI₂ cand KCI mixed in 1:1 molal ration showed ΔT_b = 2.6K. Determine the amount of each solute in 100 g of the solvent. Kb = 0.52 K Kg mole-1. Molar mass KCI = 74.5, BaCI₂ = 208.

Q. 30. K_f of benzene 4.90K kg mole^-1. 3.26g Se (Atomic mass = 78.8) in 226g of benzene showed a freezing point of 0.112⁰C lower than pure benzene. Find the molecular formula of Se.

Q. 31. A solution containing 1.017g Napthalene (Ci₀H₈) in 100g CCI₄ gave ΔT_b = 0.4⁰C. 1.24g of an unknown< solute in 100g CCI₄ gave ΔT_b = 0.62⁰C. Find molar mass of the unknown solute.

Q. 32. 1.8g glucose in 100ml solution is added to 34.2g sucrose in 100ml. Find the osmatic pressure of the resulting solution.

Q. 33. 2 grams benzoic acid (C₆H₆COOH) in 25g benzene gave ΔT_f = 1.62K. K_f = 4.9K kg mole^-1. Find the %association of benzoic acid if it exist as a dimer in solution.

Q. 34. Which of the following aqeous solution will have:-

1. Lowest freezing point
2. Highest freezing point
3. 0.1M NaCI, O.1M BaCI₂, 0.1M AI₂(SO₄)3, 0.1M Urea