Chapter 13 PROPERTIES OF SOLUTIONS Give It Some Thought Clicker Questions Chapter 13 PROPERTIES OF SOLUTIONS Lynn Mandeltort Auburn University

In the chapter-opening photograph of dye dispersing in water, is entropy increasing or decreasing? Entropy decreasing Answer: a

In the chapter-opening photograph of dye dispersing in water, is entropy increasing or decreasing? Entropy decreasing Answer: a

Why doesn’t NaCl dissolve in nonpolar solvents such as hexane, C6H14? NaCl is a polar covalent molecule and a solvent dissolves solutes that have similar intermolecular forces as the solvent. NaCl is a neutral substance and is not attracted to nonpolar hexane. NaCl is ionic and ion-ion forces in the lattice are not broken by ion-nonpolar interactions. NaCl has large ions that are hard to separate and dissolve in any solvent. Answer: c

Why doesn’t NaCl dissolve in nonpolar solvents such as hexane, C6H14? NaCl is a polar covalent molecule and a solvent dissolves solutes that have similar intermolecular forces as the solvent. NaCl is a neutral substance and is not attracted to nonpolar hexane. NaCl is ionic and ion-ion forces in the lattice are not broken by ion-nonpolar interactions. NaCl has large ions that are hard to separate and dissolve in any solvent. Answer: c

Label the following processes as exothermic or endothermic: (a) breaking solvent–solvent interactions to form separated particles (b) forming solvent–solute interactions from separated particles (a) (b) Endothermic Endothermic Endothermic Exothermic Exothermic Endothermic Exothermic Exothermic Answer: b

Label the following processes as exothermic or endothermic: (a) breaking solvent–solvent interactions to form separated particles (b) forming solvent–solute interactions from separated particles (a) (b) Endothermic Endothermic Endothermic Exothermic Exothermic Endothermic Exothermic Exothermic Answer: b

What happens if a solute is added to a saturated solution? More solute dissolves. The additional solute does not dissolve and some of the original dissolved solute comes out of the solution. The additional solute does not dissolve and the solution remains saturated. The temperature of the solution changes and some of the added solute dissolves. Answer: c

What happens if a solute is added to a saturated solution? More solute dissolves. The additional solute does not dissolve and some of the original dissolved solute comes out of the solution. The additional solute does not dissolve and the solution remains saturated. The temperature of the solution changes and some of the added solute dissolves. Answer: c

Suppose the hydrogens on the OH groups in glucose (Figure 13 Suppose the hydrogens on the OH groups in glucose (Figure 13.10) were replaced with methyl groups, CH3. Would you expect the water solubility of the resulting molecule to be higher than, lower than, or about the same as glucose? Higher solubility Lower solubility About the same solubility Answer: b

Suppose the hydrogens on the OH groups in glucose (Figure 13 Suppose the hydrogens on the OH groups in glucose (Figure 13.10) were replaced with methyl groups, CH3. Would you expect the water solubility of the resulting molecule to be higher than, lower than, or about the same as glucose? Higher solubility Lower solubility About the same solubility Answer: b

Why do bubbles form on the inside wall of a cooking pot when water is heated on the stove, even though the water temperature is well below the boiling point of water? Some water molecules break down into gases as water is heated. Dissolved gases are less soluble in solution as temperature increases. Water molecules begin to enter the gas phase to stimulate boiling. Boiling actually begins on a small scale at temperatures below the boiling point. Answer: b

Why do bubbles form on the inside wall of a cooking pot when water is heated on the stove, even though the water temperature is well below the boiling point of water? Some water molecules break down into gases as water is heated. Dissolved gases are less soluble in solution as temperature increases. Water molecules begin to enter the gas phase to stimulate boiling. Boiling actually begins on a small scale at temperatures below the boiling point. Answer: b

A solution of SO2 in water contains 0 A solution of SO2 in water contains 0.00023 g of SO2 per liter of solution. What is the concentration of SO2 in ppm? In ppb? 2.3 ppm; 2.3 × 103 ppb 23 ppm; 2.3 × 104 ppb 230 ppm: 2.30 × 105 ppb 2300 ppm; 2.300 × 106 ppb Answer: c

A solution of SO2 in water contains 0 A solution of SO2 in water contains 0.00023 g of SO2 per liter of solution. What is the concentration of SO2 in ppm? In ppb? 2.3 ppm; 2.3 × 103 ppb 23 ppm; 2.3 × 104 ppb 230 ppm: 2.30 × 105 ppb 2300 ppm; 2.300 × 106 ppb Answer: c

If an aqueous solution is very dilute, will its molality be greater than its molarity, nearly the same as its molarity, or smaller than its molarity? Molality will be greater than its molarity. Molality will be nearly the same as its molarity. Molality will be smaller than its molarity. Answer: b

If an aqueous solution is very dilute, will its molality be greater than its molarity, nearly the same as its molarity, or smaller than its molarity? Molality will be greater than its molarity. Molality will be nearly the same as its molarity. Molality will be smaller than its molarity. Answer: b

Adding 1 mol of NaCl to 1 kg of water lowers the vapor pressure of water more than adding 1 mol of C6H12O6. Explain. NaCl is highly polar whereas C6H12O6 is weakly polar and this causes the difference. NaCl has a smaller molar mass than that of C6H12O6 and this causes the difference. NaCl is polar whereas C6H12O6 is nonpolar and this causes the difference. The total solute concentration of NaCl is twice that of C6H12O6 because NaCl forms Na+ and Cl– ions and this causes the difference. Answer: d

Adding 1 mol of NaCl to 1 kg of water lowers the vapor pressure of water more than adding 1 mol of C6H12O6. Explain. NaCl is highly polar whereas C6H12O6 is weakly polar and this causes the difference. NaCl has a smaller molar mass than that of C6H12O6 and this causes the difference. NaCl is polar whereas C6H12O6 is nonpolar and this causes the difference. The total solute concentration of NaCl is twice that of C6H12O6 because NaCl forms Na+ and Cl– ions and this causes the difference. Answer: d

A solute dissolved in water causes the boiling point to increase by 0 A solute dissolved in water causes the boiling point to increase by 0.51 °C. Does this necessarily mean that the concentration of the solute is 1.0 m (Table 13.3)? Yes No Depends on whether the solute is a strong or weak electrolyte Depends on if the solute is a nonpolar, nonelectrolyte Answer: c

A solute dissolved in water causes the boiling point to increase by 0 A solute dissolved in water causes the boiling point to increase by 0.51 °C. Does this necessarily mean that the concentration of the solute is 1.0 m (Table 13.3)? Yes No Depends on whether the solute is a strong or weak electrolyte Depends on if the solute is a nonpolar, nonelectrolyte Answer: c

Of two KBr solutions, one 0. 50 m and the other 0 Of two KBr solutions, one 0.50 m and the other 0.20 m, which is hypotonic with respect to the other? The 0.20 m KCl solution is hypotonic with the 0.50 m KCl solution. The 0.50 m KCl solution is hypotonic with the 0.20 m KCl solution. Neither is hypotonic to each other. They are isotonic solutions. Answer: a

Of two KBr solutions, one 0. 50 m and the other 0 Of two KBr solutions, one 0.50 m and the other 0.20 m, which is hypotonic with respect to the other? The 0.20 m KCl solution is hypotonic with the 0.50 m KCl solution. The 0.50 m KCl solution is hypotonic with the 0.20 m KCl solution. Neither is hypotonic to each other. They are isotonic solutions. Answer: a

Is the osmotic pressure of a 0 Is the osmotic pressure of a 0.10 M solution of NaCl greater than, less than, or equal to that of a 0.10 M solution of KBr? The osmotic pressure of a 0.10 M solution of NaCl is greater than that of a 0.10 M solution of KBr. The osmotic pressure of a 0.10 M solution of NaCl is equal to that of a 0.10 M solution of KBr. The osmotic pressure of a 0.10 M solution of NaCl is less than than that of a 0.10 M solution of KBr. Answer: b

Is the osmotic pressure of a 0 Is the osmotic pressure of a 0.10 M solution of NaCl greater than, less than, or equal to that of a 0.10 M solution of KBr? The osmotic pressure of a 0.10 M solution of NaCl is greater than that of a 0.10 M solution of KBr. The osmotic pressure of a 0.10 M solution of NaCl is equal to that of a 0.10 M solution of KBr. The osmotic pressure of a 0.10 M solution of NaCl is less than than that of a 0.10 M solution of KBr. Answer: b

Some proteins reside in the hydrophobic lipid bilayer of the cell membrane. Would hydrophilic groups of these proteins still be facing the lipid “solvent”? Yes, proteins have hydrophilic groups on the exterior. No, the hydrophilic groups would be repelled by the hydrophobicity of the lipids. Answer: b

Some proteins reside in the hydrophobic lipid bilayer of the cell membrane. Would hydrophilic groups of these proteins still be facing the lipid “solvent”? Yes, proteins have hydrophilic groups on the exterior. No, the hydrophilic groups would be repelled by the hydrophobicity of the lipids. Answer: b

Why don’t oil drops stabilized by sodium stearate coagulate to form larger oil drops? Ion-dipole forces Dipole-dipole forces Dispersion forces Hydrogen bonding Answer: c

Why don’t oil drops stabilized by sodium stearate coagulate to form larger oil drops? Ion-dipole forces Dipole-dipole forces Dispersion forces Hydrogen bonding Answer: c