44) The density of solution containing 15.0 percent of ethanol (CHsOH) by mass i

Question

44) The density of solution containing 15.0 percent of ethanol (CHsOH) by mass is 0.974 gml. (a) would contain 15.0 percent of ethanol (CHsOH) by mass is Calculate the molality of this solution. (b) Calculate its molarity. (c) What volume of the solution 4.61 g of ethanol? . The 45) Calculate the molarity and the molality of an NHs solution made up of 300 g of NH in 70.0 g of water density of the solution is 0.982 gm 46) For dilute aqueous solutions in which the density of the solution is roughly equal to that of the pure solvent, the molarity of the solution is equal to its molality. Show that this statement is correct for a 0.010 M aqueous urea (NH2) CO solution 47) A 50-g sample of impure KCIO, (solubility 7.1 g per 100 g H:0 at 20 C) is contaminated with 10 percent of KCI (solubility 25.3 gper 100 g of H:0 at 20 C). Caleulate the minimum quantity of 20° C water needed to dissolve all the KCl from the sample. How mach KCIO, will be left after this treatment? (Assume that the solubilities are unaffected by the presence of the other compound) 48) The vapor pressure of benzene is 100.0 mmillg at 26.1 C. Calculate the vapor pressure of a solution containing 24.6 g of camphor (Css0) dissolved in 98.5 g of benzene. (Camphor is a low-volatility solid.) 49) The vapor pressures of ethanol (C H OH) and I-propanol (CH OH) at 35 C are 100 mmHg and 37.6 mmlig, respectively. Assume ideal behavior and calculate the partial pressures of ethanol and 1-propanol at 35 C over a solution of ethanol in 1-propanol, in which the mole fraction of ethanol is 0.300. 50) How many grams of sucrose (Ci:H220n) must be added to 552 g of water to give a solution with a vapor pressure 2.0 mmHg less than that of pure water at 20 C? (The vapor pressure of water at 20"C is 17.5 mmHg) 51) Two liquids A and B have vapor pressures of 76 mmllg and 132 mmHg, respectively, at 25 C. What is the total vapor pressure of the ideal solution made up of (a) 1.00 mole ofA and i .00 mole of B and (b) 200 moles of A and 5.00 moles of B? 52) A1 27C, the vapor pressare of pure wate is 23.76 mmltg and that of an urca solution is 22 98 mme Calculate the molality of solution 53) At 20 C, the vapor pressure of ethanol (C:HOH) is 44.0 nmbl, and the vapor pressure of methanol (CH OH) is 94.0 mmHg. A mixture of 50.0 g of methanol and S0.0 g of ethanol is prepared (and can be ate the vapor pressure of methanol and ethanol above this assumed to behave as an ideal solution). (a) Calcul solution at 20°C. (b) Calculate the mole fraction of methanol and ethanol in the vapor above this solurion a 20°C. a -nt cell atf ern

Explanation / Answer

44. 15% Ethanol solution

150 g ethanol in 1000 ml (1 L) solution

moles ethanol = 150 g/46.07 g/mol = 3.256 mol

(a) molarity = moles/L of solution

                   = 3.256 mol/L = 3.256 M

(b) mass of solution = 1000 ml x 0.974 g/ml = 974 g

mass of water = 974 - 150 = 824 g = 0.824 kg

molality = moles/kg of solvent

             = 3.256 mol/0.824 kg

             = 3.951 m

(c) 150 g Ethanol in 1000 ml solution

So,

4.61 g ethanol is present in = 4.61 g x 1000 ml/150 g = 30.73 ml

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45) moles NH3 = 30 g/17 g/mol = 1.765 mol

mass H2O = 70 g = 0.070 kg

molality of solution = 1.765 mol/0.070 kg = 25.21 m

Total mass of solution = 100 g

Volume of solution = 100 g/0.982 g/ml = 101.833 ml

molarity of solution = 1.765 mol/0.101833 L = 17.33 M

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