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Problem 57a
Brass is a substitutional alloy consisting of a solution of copper and zinc. A particular sample of red brass consisting of 80.0 % Cu and 20.0 % Zn by mass has a density of 8750 kg/m3. (a) What is the molality of Zn in the solid solution?
Problem 57b
Brass is a substitutional alloy consisting of a solution of copper and zinc. A particular sample of red brass consisting of 80.0 % Cu and 20.0 % Zn by mass has a density of 8750 kg/m3. (b) What is the molarity of Zn in the solution?
Problem 58b
Caffeine (C8H10N4O2) is a stimulant found in coffee and tea. If a solution of caffeine in the solvent chloroform (CHCl3) has a concentration of 0.0500 m, calculate (b) the mole fraction of caffeine in the solution.
Problem 61
Suppose that you want to use reverse osmosis to reduce the salt content of brackish water containing 0.22 M total salt concentration to a value of 0.01 M, thus rendering it usable for human consumption. What is the minimum pressure that needs to be applied in the permeators (Figure 13.26) to achieve this goal, assuming that the operation occurs at 298 K?
Problem 62
Assume that a portable reverse-osmosis apparatus operates on seawater, whose effective concentration (the concentration of dissolved ions) is 1.12 M, and that the desalinated water output has an effective molarity of about 0.02 M. What minimum pressure must be applied by hand pumping at 297 K to cause reverse osmosis to occur?
- You make a solution of a nonvolatile solute with a liquid solvent. Indicate whether each of the following statements is true or false. (a) The freezing point of the solution is higher than that of the pure solvent. (b) The freezing point of the solution is lower than that of the pure solvent.
Problem 63
Problem 64a
You make a solution of a nonvolatile solute with a liquid solvent. Indicate if each of the following statements is true or false.
a. The solid that forms as the solution freezes is nearly pure solute.
Problem 64b
You make a solution of a nonvolatile solute with a liquid solvent. Indicate if each of the following statements is true or false.
b. The freezing point of the solution is independent of the concentration of the solute.
- Consider two solutions, one formed by adding 10 g of glucose (C6H12O6) to 1 L of water and the other formed by adding 10 g of sucrose (C12H22O11) to 1 L of water. Calculate the vapor pressure for each solution at 20 °C; the vapor pressure of pure water at this temperature is 17.5 torr.
Problem 65
Problem 66a
a. The vapor pressure of pure water at 60°C is 149 torr. What vapor pressure is predicted by Raoult’s law for a solution at 60°C that is 50 mol % water and 50 mol % ethylene glycol (a nonvolatile solute)?
- (a) Calculate the vapor pressure of water above a solution prepared by adding 22.5 g of lactose (C12H22O11) to 200.0 g of water at 338 K. (Vapor–pressure data for water are given in Appendix B.)
Problem 67
- (b) Calculate the mass of ethylene glycol (C2H6O2) that must be added to 1.00 kg of ethanol (C2H5OH) to reduce its vapor pressure by 10.0 torr at 35 °C. The vapor pressure of pure ethanol at 35 °C is 1.00 x 10^2 torr.
Problem 68
Problem 69a
At 63.5 °C, the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. (a) What is the mole fraction of ethanol in the solution?
Problem 69b
At 63.5 °C, the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. (b) Assuming ideal solution behavior, what is the vapor pressure of the solution at 63.5 °C?
Problem 69c
At 63.5 °C, the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. (a) What is the composition in mole fraction of a solution that has a vapor pressure of 35 torr at 20 °C?
Problem 70a
At 20 °C, the vapor pressure of benzene (C6H6) is 75 torr, and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene form an ideal solution. (a) What is the composition in mole fraction of a solution that has a vapor pressure of 35 torr at 20 °C?
Problem 70b
At 20 °C, the vapor pressure of benzene (C6H6) is 75 torr, and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene form an ideal solution. (b) What is the mole fraction of benzene in the vapor above the solution described in part (a)?
Problem 73
List the following aqueous solutions in order of increasing boiling point: 0.120 m glucose, 0.050 m LiBr, 0.050 m Zn(NO3)2.
- List the following aqueous solutions in order of decreasing freezing point: 0.040 m glycerin (C3H8O3), 0.020 m KBr, 0.030 m phenol (C6H5OH).
Problem 74
Problem 75
Using data from Table 13.3, calculate the freezing and boiling points of each of the following solutions: (a) 0.22 m glycerol (C3H8O3) in ethanol, (b) 0.240 mol of naphthalene (C10H8) in 2.45 mol of chloroform, (c) 1.50 g NaCl in 0.250 kg of water, (d) 2.04 g KBr and 4.82 g of glucose (C6H12O6) in 188 g of water.
Problem 76
Using data from Table 13.3, calculate the freezing and boiling points of each of the following solutions: (a) 0.25 m glucose in ethanol; (b) 20.0 g of decane, C10H22, in 50.0 g CHCl3; (c) 3.50 g NaOH in 175 g of water, (d) 0.45 mol ethylene glycol and 0.15 mol KBr in 150 g H2O.
- How many grams of ethylene glycol (C2H6O2) must be added to 1.00 kg of water to produce a solution that freezes at -5.00 °C?
Problem 77
Problem 78
What is the freezing point of an aqueous solution that boils at 105.0 °C?
- What is the osmotic pressure formed by dissolving 44.2 mg of aspirin (C9H8O4) in 0.358 L of water at 25 °C?
Problem 79
Problem 80
Seawater contains 34 g of salts for every liter of solution. Assuming that the solute consists entirely of NaCl (in fact, over 90% of the salt is indeed NaCl), calculate the osmotic pressure of seawater at 20 °C
Problem 81
Adrenaline is the hormone that triggers the release of extra glucose molecules in times of stress or emergency. A solution of 0.64 g of adrenaline in 36.0 g of CCl4 elevates the boiling point by 0.49 °C. Calculate the approximate molar mass of adrenaline from this data.
Problem 82
Lauryl alcohol is obtained from coconut oil and is used to make detergents. A solution of 5.00 g of lauryl alcohol in 0.100 kg of benzene freezes at 4.1 °C. What is the molar mass of lauryl alcohol from these data? See Table 13.3 for the normal freezing point and 𝐾f of benzene.
Problem 83
Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g of this enzyme in 210 mL of solution has an osmotic pressure of 0.953 torr at 25 °C. What is the molar mass of lysozyme?
Problem 84
A dilute aqueous solution of an organic compound soluble in water is formed by dissolving 2.35 g of the compound in water to form 0.250 L of solution. The resulting solution has an osmotic pressure of 0.605 atm at 25 °C. Assuming that the organic compound is a nonelectrolyte, what is its molar mass?
Problem 85
The osmotic pressure of a 0.010 M aqueous solution of CaCl2 is found to be 0.674 atm at 25 °C. Calculate the van't Hoff factor, i, for the solution.