Chapter-2 Solutions
Important Questions
Topic-Wise Questions
Measuring the Concentration of Solutions
A 1.: The density of a 2.2 M solution of acetic acid (CH3COOH) in water is 1.08 gm/cc. Calculate the molality of the solution.
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A 2.: What will be the mass of a 0.5 m solution of sodium acetate in water containing 0.15 mole of sodium acetate ?
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A 3.: Calculate the mole fraction of ethanol in a sample of spirit containing 92% of ethanol by mass.
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A 4.: Calculate the mass percentage of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 g of C9H8O4 is dissolved in 450 g of CH3CN.
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A 5.: The mole fraction of methanol (CH3OH) in an aqueous solution is 0.02 and density is 0.994 gm/mL. Determine the molality and molarity of the solution.
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A 6.: A sample of toothpaste weighing 500 gm, on analysis was found to contain 0.2 gm of fluorine. Using this data calculate the concentration of fluorine in ppm.
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A 7.: Molarity of sulphuric acid solution is 18 M. If density of solution is 1.8 gm/cm3, calculate molality of solution.
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A 8.: Calculate the volume of 80% (w/w) of sulfuric acid (density 1.8 gm/mL) required to prepare one litre of 0.2 M sulfuric acid solution.
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A 9.: What is the concentration of NO3– ions when equal volumes of 0.1 M AgNO3 and 0.1 M NaCl are mixed together.
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A 10.: Calculate the density of sulfuric acid solution if its molality and molarity are 94.5 and 11.5 respectively.
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A 11.: The density of 85% sulfuric acid is 1.7 gm/cc. What is the volume of the solution which contains 17 gm of sulfuric acid ?
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A 12.: The solubility of Ba(OH)2.8H2O in water at 298 K is 5.6 gm per 100 gm of water. What is the molality of the hydroxide ion in a saturated solution of barium hydroxide at 298 K ?
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A 13.: 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.
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A 14.: Calculate mole fraction of ethyl alcohol and water in a solution containing 46 gram ethyl alcohol and 36 gram water.
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A 15.: Mole fraction of ethanol in aqueous solution is 0.25. What is the percentage concentration of ethanol by weight of the solution ?
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A 16.: Calculate the molarity and molality of 15% (w/w) solution of sulphuric acid having density 1.02 gm/cc.
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A 17.: Calculate the molality of 2.5 gm ethanoic acid (CH3COOH) in 75 gm of benzene.
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A 18.: One letter of a solution of N/2 HCl was heated in a beaker and it was observed that when the volume of solution got reduced to 600 ml, 3.25 gm of HCL was lost. Calculate the normality of the resulting solution.
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A 19.: What is molarity of the resulting solution obtained by mixing 2.5 L of 0.5 M urea solution and 500 mL of 2 M urea solution ?
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A 20.: Equal volume of 30% by mass of sulfuric acid (density 1.218 gm/cc) and 70% by mass of sulfuric acid (density 1.610 gm/cc) are mixed. If the density of the mixture is 1.425 gm/cc, Calculate the molarity and molality of the solution.
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A 21.: Two solutions of a non-electrolyte are mixed in the following manner, 480 mL of 1.5 M first solution + 520 mL of 1.2 M second solution. What is the molarity of the final solution ?
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A 22.: Calculate the number of moles of methanol (CH3OH) in 5 L of its 2 m solution if the density of solution is 0.981 kg/L.
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A 23.: Calculate the molality of a solution containing 20.7 g of K2CO3 dissolved in 500 mL of the solution (assuming density of solution = 1 g/ml)
A 24.: 20 ml of 0.2 M Al2(SO4)3 is mixed with 20 ml of 6.6 M BaCl2. Calculate the concentration of chloride ion in the solution.
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A 25.: A 6.9 M solution of KOH in water contains 30% by mass of KOH. Calculate density of KOH solution.
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A 26.: Calculate the number of molecules of oxalic acid (C2H2O4.2H2O) in 100 ml of 0.2 N oxalic acid solution.
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A 27.: 20 mL of a solution of sulfuric acid neutralised 21.2 mL of 30% solution of sodium carbonate (Na2CO3). How much water should be added to 100 ml of this solution to bring down its strength to decinormal ?
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A 28.: Calculate the molarity of a solution of CaCl2 if on chemical analysis it is found that 500 mL of CaCl2 solution contain 1.505 × 1023 Cl– ions
A 29.: 20 mL of 0.5 M HCl is mixed with 30 mL of 0.3 M HCl. Calculate the molarity of resulting solution.
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A 30.: 3.6 M sulfuric acid solution is 29% (w/w). Calculate the density of the solution.
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A 31.: Calculate the molarity of liquid HCl, if density of solution is 1.17 gm/cc.
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A 32.: Calculate the mole fraction of the solute in 1 molal aqueous solution.
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A 33.: 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.
A 34.: Battery acid is 4.27 M H2SO4 and has density of 1.25 g/ml. What is the molality of H2SO4 in the solution?
A 35.: The density of a 2.05 M acetic acid in water is 1.02 g/ml. Calculate the molality of the solution
A 36.: Calculate the mole fraction of ethylene glycol (C2H6O2) in a solution containing 20 % of C2H6O2 by mass.
A 37.: Calculate the normality of 10% (w/v) acetic acid solution.
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A 38.: 100 ml of 1 M NaOH is mixed with 50 ml of 1 N KOH solution. Calculate the normality of mixture.
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A 39.: A solution of glucose in water is labelled as 10 % (w/w). The density of the solution is 1.20 g/ml. Calculate the (a) molality (b) molarity and (c) mole fraction of each component in solution.
A 40.: Concentrated sulphuric acid has a density 1.9 g/mL and is 99 % H2SO4 by mass. Calculate the molarity of sulphuric acid.
A 41.: 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.
Solubility of Solids and Gas in Liquids
B 1.: Mole fraction of a gas in water is 0.001 at STP determine its Henry’s law constant.
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B 2.: If nitrogen gas is bubbled through water at 293 K, how many millilitres (at STP) of nitrogen would dissolve in a litter of water ? Given that the partial pressure of nitrogen is equal to 742.5 torr and KH for nitrogen is 5.75 × 107 torr.
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B 3.: If N2 gas is bubbled through water at 293 K, how many milli moles of N2 gas would dissolve in 1 litre of water. Assume that N2 exerts a partial pressure of 0.987 bar. The KH for N2 at 293 K is 76.48 k bar.
B 4.: The Henry’s law constant for the solubility of nitrogen gas in water at 298 K is 1 × 105 atm. The mole fraction of nitrogen in air is 0.8. What is the number of moles of nitrogen from the air dissolved in 10 moles of water at 298 K and 5 atm pressure ?
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B 5.: At what partial pressure, oxygen will have solubility of 0.05 g L-1 in water at 293 K? Henry’s constant (KH) for O2 in water at 293 K is 34.36 k bar. Assume the density of the solution to be same as that of the solvent.
B 6.: Air contain O2 and N2 in the ratio of 1 : 4. Calculate the ratio of solubilities in term of mole fraction of O2 and N2 dissolved in water at atmospheric pressure and room temperature at which Henry’s constant for O2 and N2 are 3.30 × 107 torr and 6.60 × 107 torr respectively.
B 7.: Henry’s Law constant of CO2 in water at 298 K is 5/3 K bar. If pressure of CO2 is 0.01 bar, Find its mole fraction.
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B 8.: The solubility of pure nitrogen gas at 25 ˚C and 1 atm is 6.8 × 10-4 mole/L. What is the concentration of nitrogen dissolved in water under atmospheric conditions ? The partial pressure of nitrogen gas in atmosphere is 0.78 atm.
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B 9.: If solubility of any gas in the liquid at 1 bar pressure is 0.05 mole/L. What will be its solubility at 3 bar pressure, keeping the temperature constant ?
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B 10.: Henry’s law constant for CO2 in water is 1.67 × 108 Pa at 298 K. Calculate the quantity of CO2 in 500 mL of soda water when packed under 2.5 atm CO2 pressure at 298 K.
B 11.: Henry’s law constant for argon is 40 K bar in water, determine molal concentration of argon in water when it is stored above water at 100 bar pressure.
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B 12.: What is the ratio of the solubilities of nitrogen and oxygen in water at 373 K, given that KH (N2) = 12.6 × 104 atm and KH (O2) = 7.01 × 104 atm. Assume that pressure ‘P’ (N2) = 0.80 atm and pressure ‘P’ (O2) = 0.20 atm.
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Vapour Pressure of Liquid Solutions
C 1.: Vapour pressure of chloroform (CHCl3) and dichloromethane (CH2Cl2) at 298 K are 200 mmHg and 415 mmHg respectively. Calculate the (a) Vapour pressure of the solution prepared by mixing 25.5 g of CHCl3 and 40 g of CH2Cl2 at 298 K and (b) Mole fraction of each component in vapour phase.
C 2.: In ideal solution of a non-volatile solute ‘B’ in solvent ‘A’ in 2 : 5 molar ratio and has vapour pressure 250 mmHg. If a another solution in ratio 3 : 4 prepared, then calculate vapour pressure above this solution.
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C 3.: The vapour pressure of an aqueous solution of glucose is 750 mmHg at 373 K. Calculate the molality and mole fraction of glucose.
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C 4.: Methanol and ethanol form nearly an ideal solution. If the vapour pressure of pure methanol and pure ethanol at 350 K are 8.1 × 104 and. 4.5 × 104 Nm-2 respectively, calculate the total vapour pressure of the solution and the mole fraction of methanol in the vapour phase if the solution contains 64 gm of methanol and 46 gm of ethanol at this temperature.
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C 5.: The vapour pressure of a dilute aqueous solution of glucose is 750 mmHg at 373 Kelvin. Calculate the mole fraction of solute if the vapour pressure of pure water is 760 mmHg at 373 K.
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C 6.: Equal moles of benzene and toluene are mixed. The vapour pressure of benzene and toluene in the pure state are 700 and 600 mmHg respectively. Calculate the mole fraction of benzene in vapour state.
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C 7.: Two liquids ‘X’ and ‘Y’ on mixing form an ideal solution. The vapour pressure of the solution containing 3 moles of ‘X’ and 1 mole of ‘Y’ is 550 mmHg. But when 4 moles of ‘X’ and 1 mole of ‘Y’ are mixed, the vapour pressure of solution thus formed is 560 mmHg. What will be the vapour pressure of the pure ‘X’ and pure ‘Y’ at this temperature.
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C 8.: Vapour pressure of CH3Cl and CH2Cl2 are 540 mmHg and 402 mmHg respectively. 101 gm of CH3Cl and 85 grams of CH2Cl2 are mixed together. Determine: (a) the vapour pressure at which the solution starts boiling (b) Molar ratio of solute versus solvent in vapour phase in equilibrium with solution.
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C 9.: The vapour pressure of ethyl acetate and ethyl propionate are 72.8 and 27.7 mmHg respectively. A solution is prepared by mixing 25 g of ethyl acetate and 50 g of ethyl propionate. Assuming the solution to be ideal, Calculate the vapour pressure of the solution.
C 10.: Calculate the mole fraction of toluene in the vapour phase, which is in equilibrium with a solution of benzene and toluene having a mole fraction of toluene 0.5. The vapor pressure of pure benzene is 119 torr and that of toluene is 37 torr at the same temperature.
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Colligative Properties
D 1.: The vapour pressure of two liquids ‘P’ and ‘Q’ are 80 and 60 torr, respectively. Calculate the total vapour pressure of solution obtained by mixing 3 mole of ‘P’ and 2 mole of ‘Q’.
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D 2.: The vapour pressure of a solution having 2 gm of solute ‘X’ (Molar mass = 32 gm/mole) in 100 gm of CS2 (P˚ = 854 torr) is 848.9 torr. Calculate molecular formula of the solute.
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D 3.: If an ideal solution is made by mixing 2 moles of benzene (P˚Benzene = 266 mmHg) and 3 moles of another liquid (P˚Liquid = 236 mmHg). The total vapour pressure of the solution at the same temperature would be :
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D 4.: Two components in the ratio of X : Y forms an azeotropic mixture. They are mixed in the ratio of X : 2Y. How many moles one of the pure component ‘Y’ will be evaporate before getting azeotropic solution ?
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D 5.: What weight of solute is required to dissolve in 180 gm of water to reduce the vapour pressure to 4/5th of pure water ? Given, molecular mass of solute is 60.
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D 6.: At 298 K, the vapour pressure of pure benzene is 0.256 bar and vapour pressure of pure toluene is 0.925 bar. If the mole fraction of benzene in solution is 0.40, find the total vapour pressure of solution. Also find the mole fraction of toluene in vapour phase.
D 7.: The vapour pressure of a pure liquid at 25 ˚C is 100 mmHg. Calculate the relative lowering of vapour pressure if the mole fraction of solvent in solution is 0.8.
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D 8.: The vapour pressure of pure liquids A and B are 450 and 700 mmHg respectively, at 350 K. Find out the composition of the mixture if total vapour pressure is 600 mmHg. Also find the composition of the vapour phase.
D 9.: For a solution if P˚A is 600 mmHg and P˚B is 840 mmHg under atmospheric conditions and vapour pressure of solution is 1 atm then find: (a) Composition of solution (b) Composition of vapour on equilibrium with solution.
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D 10.: An aqueous solution of glucose is made by dissolving 10 gram of glucose in 90 grams of water at 303 K. If the vapour pressure of pure water at 303 K is 32.8 mmHg, what would be the vapour pressure of the solution.
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D 11.: The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile and non-electrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g/mol). The vapour pressure of the solution then is 0.845 bar. What is the molar mass of the solid substance?
D 12.: A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20 °C are 440 mmHg for pentane and 120 mmHg for hexane. Calculate the mole fraction of pentane in vapour phase.
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D 13.: Vapour pressure of water is 360 mmHg. How much urea (NH2CONH2) should be added to 200 mL water to reduce its vapour pressure by 0.5% ?
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D 14.: How much urea (NH2CONH2) must be dissolved in 50 gm of water so that the vapour pressure at room temperature is reduced by 25% ? Also calculate the molarity of the solution obtained.
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D 15.: The vapour pressure of 2.1 % of an aqueous solution of non-electrolyte at 373 K is 755 mm. Calculate the molar mass of solute. (Consider that vapour pressure of water at 373 K is 760 mm).
D 16.: An ideal solution was obtained by mixing methanol and ethanol. If the partial vapour pressure of methanol and ethanol are 2.619 kPa and 4.556 kPa respectively, then calculate the composition of vapour (in terms of mole fraction).
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D 17.: Find the molality of a solution containing on non-volatile solute if its vapour pressure is 2% below the vapour pressure of pure water.
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D 18.: The vapour pressure of 2.1% of an aqueous solution of non-volatile solute at 373 K is 755 mmHg. Calculate the molar mass of the solute.
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D 19.: 20 g of solute was added to 100 g of water at 25 ˚C. The vapour pressure of water and that of the solution were 23.76 mmHg and 22.41 mmHg respectively at that temperature. Calculate the relative molecular mass of the solute.
D 20.: The solution of 2.5 gm of a non-volatile substance in 100 gm of benzene boiled at a temperature 0.42 ˚C higher than the boiling point of pure benzene. Calculate molar mass of the substance. Given Kb of benzene is 2.67 K kg mole-1.
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D 21.: A solution of urea (molar mass = 60 gm/mole) boils at 100.18 ˚C at the atmospheric pressure. If Kb and Kf for water are 1.86 and 0.512 ˚C/molal respectively, calculate freezing point of the solution.
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D 22.: A solution of glycerol (C3H8O3), in water was prepared by dissolving some glycerol in 500 g of water. This solution has a boiling point of 100.42 ˚C. What mass of glycerol was dissolved to make the solution? Kb for water = 0.52 K kg/mole.
D 23.: The boiling point of pure acetone is 56.38 ˚C. When 0.71 gram of a compound is dissolved in 10 gm of acetone, there is elevation of 56.88 ˚C in boiling point. What is the molar mass of the compound ? Given, Kb of acetone is 1.72 K kg mole-1.
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D 24.: Calculate the boiling point of a solution containing 0.456 gram of camphor (molecular mass = 152 gm/mole) dissolved in 31.4 gram of acetone (boiling point = 329.45 K). Given that the molecular elevation constant per 100 gm of solvent is 17.2 K.
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D 25.: 18 g of glucose, C6H12O6, is dissolved in 1 kg of water. At what temperature will the water boil at 1.013 bar pressure ? Kb for water is 0.52 K kg/mole.
D 26.: The boiling point of benzene is 353.23 K. When 1.80 g of a non-volatile solute was dissolved in 90 g of benzene, the boiling point is raised to 354.11 K. Calculate the molar mass of the solute. Kb for benzene is 2.53 K kg/mole.
D 27.: Calculate the molal elevation constant of water if molar enthalpy of vaporization of water at 373 K is 40.585 kJ/mole.
D 28.: 45 g of ethylene glycol (C2H6O2) is mixed with 600 g water. Calculate : (a) freezing point of depression (b) freezing point of solution. (Kf for H2O = 1.86 K kg/mole)
D 29.: An aqueous solution has 5% urea (NH2CONH2) and 10% glucose (C6H12O6) by weight. What will be the freezing point of this solution ? Given, Kf of water is 1.86 K kg mole-1.
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D 30.: What mass of ethylene glycol (Molecular mass = 62.0 g/mol) must be added to 5.50 kg of water to lower the freezing point of water from 0 ˚C to -10.0 ˚C. (Kf H2O is 1.86 K kg/mole).
D 31.: Calculate the amount of ice which will separate on cooling a solution to -9.3 ˚C containing 50 gm of ethylene glycol in 200 gm of water (Kf for water = 1.86 K kg mole-1).
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D 32.: 1.00 g of non-electrolyte solute dissolved in 50 g of benzene lowered the freezing point of benzene by 0.40 K. Kf of benzene is 5.12 K kg/mole. Find Molar mass of solute.
D 33.: 1 gm of a non-electrolyte solute (molar mass 250 gm/mole) was dissolved in 51.2 gm of benzene. If the freezing point depression constant, Kf of benzene is 5.12 K kg mole-1, then, calculate the freezing point of benzene.
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D 34.: The normal freezing point of nitrobenzene (C6H5NO2) is 278.82 K. A 0.25 molal solution of a certain solute in nitrobenzene causes a freezing point depression of 2 ˚C. Calculate the value of Kf for Nitrobenzene.
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D 35.: A solution of sucrose (molar mass = 342 gm/mole) is prepared by dissolving 68.4 gm in 1000 gm of water. What is the freezing point and boiling point of solution ? (Kf for water is 1.86 K/m and Kb for water is 0.52 K/m)
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D 36.: 200 cm3 of an aqueous soln of protein contains 1.26 g of protein. Osmotic pressure of this solution at 300 K is found to be 2.57 × 10-3 bar. Calculate molecular mass of protein.
D 37.: 10 g of a substance were dissolved in water and solution was made up to 250 cm3. Osmotic pressure of solution was found to be 8 105 Nm-2 at 288 K. Find molar mass of solute.
D 38.: 3% solution of glucose is isotonic with 1% solution of a non-volatile non electrolyte substance. The molecular mass of the substance would be :
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D 39.: One litre of aqueous solution of sucrose (molar mass = 342 gm/mole) weighing 1015 gm is found to record an osmotic pressure of 4.82 atm at 298 K. What is the molality of the solution ?
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D 40.: A solution containing 10 gm per dm3 of urea (molar mass = 60 gm/mole) is isotonic with a 5% solution of a non-volatile and non-electrolyte solute. Calculate the molecular mass of the solute.
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D 41.: 100 mg of a protein was dissolved in just enough water to make 10 mL of the solution. If the solution has an osmotic pressure of 13.3 mmHg at 25 ˚C, what is the molar mass of the protein? (R = 0.0821 L atm mole-1 K-1)
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D 42.: Calculate osmotic pressure of solution containing 0.6 gm urea (NH2CONH2) and 3.42 gm sugar (C12H22O11) in 100 ml of H2O at 27 ˚C.
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D 43.: The osmotic pressure of blood is 8.21 atm at 37 ˚C. How much glucose would be used for an injection that is at the same osmotic pressure as blood ? (R= 0.0821 atm mole-1 K-1]
D 44.: At what concentration of solute ‘P’ (molar mass = 342 gm/mole) the solution will be isotonic with a 5% solution of urea ?
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D 45.: A 5% (w/v) solution of cane sugar (molar mass = 342 gm/mole) is isotonic with 1% (w/v) solution of a substance ‘X’. Calculate the molecular mass of ‘X’.
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D 46.: Calculate the osmotic pressure of a solution obtained by mixing 100 mL of 4.5% solution of urea (molar mass = 60 gm/mole) and 100 ml of 3.42% solution of cane sugar (molar mass = 342 gm/mole) at 300 K. (Given; R = 0.0821 L atm K-1 mole-1)
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D 47.: At 300 K, 36 gm of glucose present per litre of the solution has an osmotic pressure of 4.98 bar. If the osmotic pressure of the solution is 1.52 bar at the same temperature, what would be its concentration ?
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D 48.: Find the osmotic pressure of M/20 solution of urea at 27 °C (Given; R = 0.0821 L atm K-1 mole-1).
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Abnormal Molar Masses and Van’t Hoff factor
E 1.: 2 gm of benzoic acid (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mole–1. What is the percentage association of acid if it forms dimer in solution?
E 2.: 0.6 mL of acetic acid having density of 1.06 gm/ml is dissolved in 1 Litre of water. The depression in freezing point observed for this strength of the acid was 0.0205 °C. Calculate the Van’t Hoff factor and the dissociation constant of the acid. Kf for water = 1.86 K Kg mol-1.
E 3.: 0.5 gm KCl was dissolved in 100 gm water and the solution originally at 0 °C, froze at -0.24 °C. Calculate the percentage ionization of salt. Kf for water = 1.86 K Kg mol-1.
E 4.: Calculate the freezing point depression expected for 0.0711 molal aqueous solution of Na2SO4. If this solution actually freezes at 0.32 °C, What would be the value of Van’t Hoff factor ? Kf for water = 1.86 K Kg mol-1.
E 5.: 200 mL of an aqueous solution of a protein contains its 1.26 gm. The osmotic pressure of this solution at 300 K is found to be 2.57 × 10-3 bar. Calculate the molar mass of protein (R = 0.083 L bar mole-1 K-1).
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E 6.: What would be the osmotic pressure of 25 ˚C of an aqueous solution containing 1.95 gram of sucrose (C12H22O11) present in 150 mL of solution ?
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E 7.: In a solvent 50% of benzoic acid dimerises while rest ionises, determine molar mass of acid which is observed and its Van’t Hoff factor.
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E 8.: What is the boiling point of 1 molal aqueous solution of NaCl, if Kb for water is 0.52 K kg mole-1 ?
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E 9.: The boiling point of water at 735 torr is 99.07 ˚C. Calculate the mass of NaCl added in 100 gm water to make it’s boiling point 100 ˚C (Kb = 0.51 K kg mole-1).
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E 10.: A 0.002 molal aqueous solution of an ionic compound Co(NH3)5(NO2)Cl freezes at -0.00732 ˚C. Calculate the number of moles of ions produced by the compound in aqueous solution (Kf = 1.86 ˚C/molal).
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E 11.: What mass of NaCl must be dissolved in 65 gm of water to lower the freezing point by 7.5 °C ? Kf for water = 1.86 K Kg mol-1. Assuming that Van’t Hoff factor for NaCl is 1.87.
E 12.: Calculate the boiling point of a solution prepared by adding 15 gm of NaCl to 250 gm of water (Kb for water = 0.52 K Kg mol-1).
E 13.: Van’t Hoff factor for SrCl2 at 0.01 molal concentration is 1.6, calculate percentage of ionization of SrCl2.
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E 14.: What is the freezing point of 0.4 molal solution of acetic acid in benzene in which it dimerises to the extent of 85%. Freezing point of benzene is 278.4 K and its molar heat of fusion is 10.042 kJ/mole.
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E 15.: K4[Fe(CN)6] is supposed to be 40% dissociated when 1 M solution prepared. Its boiling point is equal to another 20% (w/v) solution of non-electrolyte substance ‘A’. Calculate the molecular mass of ‘A’, considering molality = molarity.
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E 16.: A solution contains 0.896 gm of potassium sulphate (K2SO4) in 500 mL. Its osmotic pressure is found to be 0.69 atm at 27 ˚C. Calculate the value of Van’t Hoff factor.
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E 17.: Calculate the boiling point of a solution containing 0.61 gm of benzoic acid in 5 gm of carbon disulphide (CS2) assuming 84% dimerization of acid. The boiling point and Kb of carbon disulphide (CS2) are 46.2 ˚C and 2.3 K/molal respectively.
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E 18.: If any solute ‘A’ dimerises in water at 1 atm pressure and the boiling point of this solution is 100.52 ˚C if 2 moles of A is added to 1 Kg of water. Kb for water is 0.52 ˚C/molal. Calculate the percentage of association of ‘A.’
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E 19.: A 0.1 molal aqueous solution of a weak acid is 30% ionized. If Kf for water is 1.86 °C/molal, then, calculate the freezing point of the solution.
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E 20.: Calculate the amount of sodium chloride which must be added to one kilogram of water so that the freezing point of the solution is depressed by 3 K. (Kf for water = 1.86 K/molal)
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E 21.: Calculate the boiling point of one molar aqueous solution (density = 1.04 gm/mL) of potassium chloride. (Kb for water = 0.52 K/molal)
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E 22.: In a 0.2 molar aqueous solution of a weak acid HX, the degree of ionization is 0.3. Calculate the freezing point of the solution.
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E 23.: A 1.0 gm of substance of molecular formula AB2 when dissolved in 25 gm of benzene reduced the freezing point by 1.6 ˚C while 1.0 gm of substance AB3 on mixing with the same amount of benzene depressed the freezing point by 1.25 ˚C. Determine the atomic mass of ‘A’ and ‘B’. (Kf for benzene = 5.1 K/molal).
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E 24.: 75.2 gm of phenol (C6H5OH) is dissolved in solvent of Kf = 14 K/molal. If depression in freezing point is 7 K, find the percentage of phenol that dimerises.
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E 25.: A solution of 2.5 gm of ‘A’ in 100 gm of water lowers the freezing point by 0.3 °C. Substance ‘A’ tetra-merises in water to the extent of 80%. Calculate the molecular mass of ‘A’ (Kf for water = 1.86 K/molal)
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E 26.: 17.4% potassium sulphate (K2SO4) solution at 27 ˚C is isotonic with 4% NaOH solution at the same temperature. If NaOH is 100% ionised, what is the degree of ionization of potassium sulphate in aqueous solution ?
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E 27.: An aqueous solution containing 1.248 gm of barium chloride (molar mass = 208.34 gm/mole) in 100 gm of water boils at 100.0832 ˚C. Calculate degree of dissociation of barium chloride. (Kb for water = 0.52 K/molal)
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Theoretical Questions
P 1.: Explain the solubility rule “like dissolve like” in term of intermolecular forces that exist in solutions.
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P 2.: Why are aquatic species more comfortable in cold water in comparison to warm water ?
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P 3.: Why is the vapour pressure of a solution of non-volatile solute lower than that of water ?
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P 4.: Explain why on adding of 1 mole of NaCl to 1 L of water, the boiling point of water increases, while addition of 1 mole of methyl alcohol to 1 L of water decreases its boiling point.
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P 5.: Explain why molality and mole fraction are independent of temperature while molarity is a function of temperature ?
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P 6.: Why is it not possible to obtain pure ethanol by fractional distillation ? What general name is given to binary mixture which show deviation from Raoult’s law and whose component cannot be separated by fractional distillation ? How many types of such mixtures are there ?
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P 7.: How can you remove the hard calcium carbonate layer of the egg without damaging its semi-permeable membrane ? Can this egg be inserted into a bottle with a narrow neck without distorting its shape ? Explain the process involved.
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P 8.: Why is the mass determined by measuring a colligative property in case of some solutes is abnormal ? Discuss it with the help of Van’t Hoff factor.
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P 9.: Which aqueous solution has higher concentration; one molar or one molal having the same solute ?
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P 10.: Will elevation in boiling point temperature be same for 0.1 molar NaCl and 0.1 molar sucrose solution ?
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P 11.: What is the expected deviation from ideal solution behaviour when acetone and chloroform are mixed to form a solution ?
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P 12.: When 50 ml of ethanol and 50 ml of water are mixed, predict whether the volume of the solution is equal to, greater than, or less than 100 ml.
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P 13.: Certain solids dissolve in water with the evolution of heat, while a few other dissolve with the absorption of heat. Explain.
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P 14.: Out of 1M H2SO4 and 1N H2SO4, which is more concentrated and why ?
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P 15.: Why dissolution of some solid compounds is exothermic while that of some others is endothermic ?
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P 16.: 4% NaOH solution (w/v) and 6% urea solution (w/v) are equimolar but not isotonic. Explain.
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P 17.: At the same temperature, why is hydrogen gas more soluble in water as compared to helium ?
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P 18.: What is the difference between molal elevation constant and molecular elevation constant ?
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P 19.: A doctor advised a person suffering from high blood pressure to take less quantity of salt. Explain.
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P 20.: Is it advisable to use ethylene glycol in car radiators during summer ?
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P 21.: Discuss the effect of temperature on the solubility of Na2SO4.10H2O (Glauber’s salt) in water.
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P 22.:Define osmotic pressure and describe Berkeley and Hartley’s method for the determination of osmotic pressure.
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