1. How many grams of NaCl must be dissolved in 100. g of water to make a solution of 3.46 m in NaCl?
2. A solution is prepared by mixing 16.0 g of CH3OH and 50.0 g of water. (a) What is the mass percent of methanol in the solution? (b) what is the mole fraction of each component in the solution? (c) If the density of solution is 0.955 g/mL, what is the molarity and molality of CH3OH, respectively, in the solution?
3. The solubility of H2S gas in water at 20 oC and 1 atm pressure is 258 mL (measured at STP) per 100 g H2O. (a) What is the mass percent of dissolved H2S? (b) What is the molality of the H2S solution? (c) What is the solubility of H2S gas expressed in mL of H2S (at STP) per 100 g H2O when the temperature is 20 oC and the partial pressure of the gas is 255 torr?
4. Benzene and toluene form an ideal solution at all proportion. The vapor pressure of pure benzene and pure toluene at 25 oC are 95.1 and 28.4 mmHg, respectively. What is the vapor pressure of a solution that contains 50.0 g benzene (mw 78.11) and 50.0 g toluene (mw 92.13)? What is the composition of the vapor that is in equilibrium with the above benzene-toluene solution at 25 oC?
5. Styrene (C8H8) and ethylbenzene (C8H10) form ideal mixture. If a mixture is composed of 38% styrene and 62% ethylbenzene, by mass, at 90oC, what is the composition of the vapor in equilibrium with the liquid mixture. The vapor pressure of styrene and ethylbenzene at 90oC are 134 mmHg and 182 mmHg, respectively.
6.Calculate the vapor pressure lowering, P, when 10.0 mL of glycerol (C3H8O3) is added to 500.0 mL of water at 50.oC. At this temperature, the vapor pressure of pure water is 92.5 torr and its density is 0.988 g/mL. The density of glycerol is 1.26 g/mL.
7. A radiator fluid mixture contains 3.00 kg of antifreeze ethylene glycol (C2H6O2) and 2.50 kg of water. What is the boiling and freezing points of the solution? (For water, Kf = 1.86 oC/m; Kb = 0.512 oC/m)
8. What is the minimum concentration of ethylene glycol (C2H6O2) solution that will protect the cooling system from freezing at 0.0oC?
9. When 1.921 g of nicotine is completely dissolved in 48.92 g of water, the solution freezes at -0.450 oC. (a) Calculate the molality of the solution. (b) What is the molar mass of nicotine? (c) If nicotine has the composition 74.0% C, 8.70% H and 17.3 % N, by mass, determine its empirical and molecular formula.
10.If a solution contains 10.5 g of sucrose (C12H22O11) per 100. mL, what is its osmotic pressure at 25 oC. What concentration (in g/100. mL solution) of salt (NaCl) would exhibit the same osmotic pressure. (Assume NaCl dissociates completely.)
11. A 50.0 mL sample of an aqueous solution containing 1.08 g of human serum albumin (HSA) has an osmotic pressure of 5.85 mmHg at 298 K. Calculate the molar mass of HSA.
2. A solution is prepared by mixing 16.0 g of CH3OH and 50.0 g of water. (a) What is the mass percent of methanol in the solution? (b) what is the mole fraction of each component in the solution? (c) If the density of solution is 0.955 g/mL, what is the molarity and molality of CH3OH, respectively, in the solution?
3. The solubility of H2S gas in water at 20 oC and 1 atm pressure is 258 mL (measured at STP) per 100 g H2O. (a) What is the mass percent of dissolved H2S? (b) What is the molality of the H2S solution? (c) What is the solubility of H2S gas expressed in mL of H2S (at STP) per 100 g H2O when the temperature is 20 oC and the partial pressure of the gas is 255 torr?
4. Benzene and toluene form an ideal solution at all proportion. The vapor pressure of pure benzene and pure toluene at 25 oC are 95.1 and 28.4 mmHg, respectively. What is the vapor pressure of a solution that contains 50.0 g benzene (mw 78.11) and 50.0 g toluene (mw 92.13)? What is the composition of the vapor that is in equilibrium with the above benzene-toluene solution at 25 oC?
5. Styrene (C8H8) and ethylbenzene (C8H10) form ideal mixture. If a mixture is composed of 38% styrene and 62% ethylbenzene, by mass, at 90oC, what is the composition of the vapor in equilibrium with the liquid mixture. The vapor pressure of styrene and ethylbenzene at 90oC are 134 mmHg and 182 mmHg, respectively.
6.Calculate the vapor pressure lowering, P, when 10.0 mL of glycerol (C3H8O3) is added to 500.0 mL of water at 50.oC. At this temperature, the vapor pressure of pure water is 92.5 torr and its density is 0.988 g/mL. The density of glycerol is 1.26 g/mL.
7. A radiator fluid mixture contains 3.00 kg of antifreeze ethylene glycol (C2H6O2) and 2.50 kg of water. What is the boiling and freezing points of the solution? (For water, Kf = 1.86 oC/m; Kb = 0.512 oC/m)
8. What is the minimum concentration of ethylene glycol (C2H6O2) solution that will protect the cooling system from freezing at 0.0oC?
9. When 1.921 g of nicotine is completely dissolved in 48.92 g of water, the solution freezes at -0.450 oC. (a) Calculate the molality of the solution. (b) What is the molar mass of nicotine? (c) If nicotine has the composition 74.0% C, 8.70% H and 17.3 % N, by mass, determine its empirical and molecular formula.
10.If a solution contains 10.5 g of sucrose (C12H22O11) per 100. mL, what is its osmotic pressure at 25 oC. What concentration (in g/100. mL solution) of salt (NaCl) would exhibit the same osmotic pressure. (Assume NaCl dissociates completely.)
11. A 50.0 mL sample of an aqueous solution containing 1.08 g of human serum albumin (HSA) has an osmotic pressure of 5.85 mmHg at 298 K. Calculate the molar mass of HSA.
Answers & Comments
Answer:
1.To calculate the grams of NaCl needed to make a 3.46 M solution, we need to use the formula:
moles of solute = (mass of solute in grams) / (molar mass of solute)
Molarity (M) = moles of solute / liters of solution
Rearranging the second equation, we get:
moles of solute = Molarity (M) x liters of solution
We know the molarity and the volume, so we can calculate the moles of NaCl needed:
moles of NaCl = 3.46 mol/L x 0.1 L = 0.346 mol
The molar mass of NaCl is 58.44 g/mol, so we can calculate the mass needed:
mass of NaCl = 0.346 mol x 58.44 g/mol = 20.2 g
Therefore, we need 20.2 grams of NaCl to make a solution of 3.46 M in NaCl.
2.(a) The mass percent of methanol in the solution is:
mass percent = (mass of solute / total mass of solution) x 100%
mass of solute = 16.0 g
total mass of solution = 16.0 g + 50.0 g = 66.0 g
mass percent = (16.0 g / 66.0 g) x 100% = 24.24%
(b) The mole fraction of each component can be calculated using the following formula:
mole fraction = (moles of component / total moles of solution)
To calculate the moles of each component, we need to use their masses and molar masses:
moles of CH3OH = 16.0 g / 32.04 g/mol = 0.499 mol
moles of H2O = 50.0 g / 18.02 g/mol = 2.776 mol
Now we can calculate the mole fraction of each component:
mole fraction of CH3OH = 0.499 mol / (0.499 mol + 2.776 mol) = 0.152
mole fraction of H2O = 2.776 mol / (0.499 mol + 2.776 mol) = 0.848
(c) The molarity of CH3OH can be calculated using the following formula:
Molarity (M) = moles of solute / liters of solution
We know the moles of CH3OH and the volume of the solution:
Molarity (CH3OH) = 0.499 mol / 0.066 L = 7.56 M
To calculate the molality, we need to use the mass of solvent (water) in kg:
mass of solvent = 50.0 g / 1000 = 0.050 kg
molality = moles of solute / mass of solvent in kg
molality (CH3OH) = 0.499 mol / 0.050 kg = 9.98 mol/kg
3.(a) The solubility of H2S gas in water is given as 258 mL (measured at STP) per 100 g H2O. To calculate the mass percent of dissolved H2S, we need to know the volume of H2S gas dissolved in the water:
mass percent = (mass of H2S / mass of solution) x 100%
mass of H2S = (volume of H2S gas at STP) x (density of H2S gas at STP) x (molar mass of H2S)
mass of solution = mass