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Problem 21b
Two nonpolar organic liquids, hexane (C6H14) and heptane (C7H16), are mixed. (b) Hexane and heptane are miscible with each other in all proportions. In making a solution of them, is the entropy of the system increased, decreased, or close to zero, compared to the separate pure liquids?
Problem 22
KBr is relatively soluble in water, yet its enthalpy of solution is + 19.8 kJ/mol. Which of the following statements provides the best explanation for this behavior? (a) Potassium salts are always soluble in water. (b) The entropy of mixing must be unfavorable. (c) The enthalpy of mixing must be small compared to the enthalpies for breaking up water–water interactions and K–Br ionic interactions. (d) KBr has a high molar mass compared to other salts like NaCl.
- The solubility of Cr1NO323 # 9 H2O in water is 208 g per 100 g of water at 15 °C. A solution of Cr1NO323 # 9 H2O in water at 35 °C is formed by dissolving 324 g in 100 g of water. When this solution is slowly cooled to 15 °C, no precipitate forms. (b) You take a metal spatula and scratch the side of the glass vessel that contains this cooled solution, and crystals start to appear. What has just happened?
Problem 23
- The solubility of MnSO4 · H2O in water at 20 °C is 70 g per 100 mL of water. (b) Given a solution of MnSO4 · H2O of unknown concentration, what experiment could you perform to determine whether the new solution is saturated, supersaturated, or unsaturated?
Problem 24
Problem 25c
By referring to Figure 13.15, determine whether the addition of 40.0 g of each of the following ionic solids to 100 g of water at 40 °C will lead to a saturated solution:(c) K2Cr2O7
Problem 25d
By referring to Figure 13.15, determine whether the addition of 40.0 g of each of the following ionic solids to 100 g of water at 40 °C will lead to a saturated solution: (d) Pb(NO3)2.
Problem 26b
By referring to Figure 13.15, determine the mass of each of the following salts required to form a saturated solution in 250 g of water at 30 °C: (b) Pb(NO3)2,
Problem 26c
By referring to Figure 13.15, determine the mass of each of the following salts required to form a saturated solution in 250 g of water at 30 °C: (c) Ce2(SO4)3.
- Consider water and glycerol, CH2(OH)CH(OH)CH2OH. (b) List the intermolecular attractions that occur between a water molecule and a glycerol molecule.
Problem 27
Problem 28
Oil and water are immiscible. Which is the most likely reason? (a) Oil molecules are denser than water. (b) Oil molecules are composed mostly of carbon and hydrogen. (c) Oil molecules have higher molar masses than water. (d) Oil molecules have higher vapor pressures than water. (e) Oil molecules have higher boiling points than water.
- Common laboratory solvents include acetone (CH3COCH3), methanol (CH3OH), toluene (C6H5CH3), and water. Which of these is the best solvent for nonpolar solutes?
Problem 29
Problem 33
Which of the following in each pair is likely to be more soluble in hexane, C6H14: (a) CCl4 or CaCl2, (b) benzene (C6H6) or glycerol, CH2(OH)CH(OH)CH2OH, (c) octanoic acid, CH3CH2CH2CH2CH2CH2CH2COOH, or acetic acid, CH3COOH? Explain your answer in each case.
Problem 34a
Which of the following in each pair is likely to be more soluble in water: (a) cyclohexane (C6H12) or glucose (C6H12O6),
Problem 34b
Which of the following in each pair is likely to be more soluble in water: (b) propionic acid (CH3CH2COOH) or sodium propionate (CH3CH2COONa)
Problem 34c
Which of the following in each pair is likely to be more soluble in water: (c) HCl or ethyl chloride (CH3CH2Cl)? Explain in each case.
Problem 35c
Indicate whether each statement is true or false: (c) As you cool a saturated solution from high temperature to low temperature, solids start to crystallize out of solution if you achieve a supersaturated solution.
Problem 35d
Indicate whether each statement is true or false: (d) If you take a saturated solution and raise its temperature, you can (usually) add more solute and make the solution even more concentrated.
- Indicate whether each statement is true or false: (c) The solubility of most gases in water decreases as the temperature increases because water is breaking its hydrogen bonding to the gas molecules as the temperature is raised.
Problem 36
- The Henry’s law constant for helium gas in water at 30 °C is 3.7 * 10^-4 M/atm and the constant for N2 at 30 °C is 6.0 * 10^-4 M/atm. If the two gases are each present at 1.5 atm pressure, calculate the solubility of each gas.
Problem 37
- The partial pressure of O2 in air at sea level is 0.21 atm. Using the data in Table 13.1, together with Henry’s law, calculate the molar concentration of O2 in the surface water of a mountain lake saturated with air at 20 °C and an atmospheric pressure of 650 torr.
Problem 38
Problem 39a
(a) Calculate the mass percentage of Na2SO4 in a solution containing 10.6 g of Na2SO4 in 483 g of water.
Problem 39b
(b) An ore contains 2.86 g of silver per ton of ore. What is the concentration of silver in ppm?
- A solution is made containing 14.6 g of CH3OH in 184 g of H2O. Calculate (a) the mole fraction of CH3OH.
Problem 41
Problem 42a
A solution is made containing 20.8 g of phenol (C6H5OH) in 425 g of ethanol (CH3CH2OH). Calculate (a) the mole fraction of phenol,
Problem 42c
A solution is made containing 20.8 g of phenol (C6H5OH) in 425 g of ethanol (CH3CH2OH). Calculate (c) the molality of phenol.
Problem 43a,b
Calculate the molarity of the following aqueous solutions: (a) 0.540 g of Mg(NO3)2 in 250.0 mL of solution, (b) 22.4 g of LiClO4 • 3 H2O in 125 mL of solution,
Problem 43c
Calculate the molarity of the following aqueous solutions: (c) 25.0 mL of 3.50 M HNO3 diluted to 0.250 L.
Problem 44b
What is the molarity of each of the following solutions: (b) 5.25 g of Mn(NO3)2⋅2H2O in 175 mL of solution,
Problem 44c
What is the molarity of each of the following solutions: (c) 35.0 mL of 9.00 M H2SO4 diluted to 0.500 L?
- Suppose that one wishes 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 render- ing it usable for human consumption. What is the mini- mum pressure that needs to be applied in the permeators (Figure 18.20) to achieve this goal, assuming that the oper- ation occurs at 298 K? (Hint: Refer to Section 13.5.)
Problem 45