Question 1

At a given temperature,the vapor pressures of hexane and octane are 183 mm Hg and 59.2 mm Hg,respectively.Calculate the total vapor pressure over a solution of hexane and octane.The mole fraction of hexane (X_hexane)is 0.580. A) 106 mm Hg B) 121 mm Hg C) 131 mm Hg D) 242 mm Hg

Accepted Answer

The total vapor pressure is given by the equation: Ptotal = X_hexaneP1 + (1 - X_hexane)P2 where P1 and P2 are the vapor pressures of hexane and octane, respectively. Substituting the given values: Ptotal = (0.580)(183 mm Hg) + (1- 0.580)(59.2 mm Hg) Ptotal = 106.14 mm Hg ≈ 131 mm Hg Therefore, the best choice is C.

Question 2

Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water.The molal-freezing-point-depression constant (K_f)for water is 1.86°C/m. A) -0.45°C B) +0.45°C C) -0.23°C D) +0.23°C E) 1.23°C

Accepted Answer

First, calculate the moles of KCl: $ \frac{5.0 \, \text{g}}{74.55 \, \text{g/mol}} = 0.067 \, \text{moles} $. KCl dissociates into 2 ions (K+ and Cl-), so the total moles of particles is $ 0.067 \, \text{moles} \times 2 = 0.134 \, \text{moles} $. The molality (m) is moles of solute per kilogram of solvent, so $ \frac{0.134 \, \text{moles}}{0.550 \, \text{kg}} = 0.244 \, \text{m} $. The freezing point depression is $ \Delta T_f = i \cdot K_f \cdot m = 1 \cdot 1.86^\circ C/m \cdot 0.244 \, \text{m} = 0.454 \, \text{°C} $. Since it's a depression, the freezing point lowers, hence -0.45°C.

Question 3

Calculate the freezing point of a solution of 40.0 g methyl salicylate,C₇H₆O₂,dissolved in 800.g of benzene,C₆H₆.K_f for benzene is 5.10°C/m and the freezing point is 5.50°C for benzene. A) -2.09°C B) 2.09°C C) 3.41°C D) 7.59°C

Accepted Answer

The answer of Calculate the freezing point of a solution...

Question 4

Place the following aqueous solutions of nonvolatile,nonionic compounds in order of decreasing osmotic pressure. I.0.011 M ethanol II.0.00095 M fructose III.0.0060 M glycerin
A) I > III > II
B) I > II > III
C) II > III > I
D) III > I > II
E) II > I > III

Accepted Answer

Osmotic pressure is directly proportional to the molarity of the solution. Therefore, the solution with the highest molarity will have the highest osmotic pressure, and the one with the lowest molarity will have the lowest osmotic pressure. The order from highest to lowest molarity (and thus osmotic pressure) is: 0.011 M ethanol (I) > 0.0060 M glycerin (III) > 0.00095 M fructose (II).

Question 5

What is the expected freezing point of a 0.50 m solution of Li₂SO₄ in water? K_f for water is 1.86°C/m. A) -0.93°C B) -1.9°C C) -2.8°C D) -6.5°C E) +1.9°C

Accepted Answer

We first need to calculate the van't Hoff factor, i. Each Li₂SO₄ molecule dissociates into 2 ions (Li+ and SO42-), so i = 2. Next, we calculate the molality of the solution: molality = moles of solute / mass of solvent (in kg) To find the moles of solute, we need to know the molar mass of Li₂SO₄: Molar mass of Li2SO4 = 2(6.941 g/mol) + 1(32.06 g/mol) + 4(15.999 g/mol) = 109.94 g/mol 1 mol of Li2SO4 = 109.94 g So, 0.50 m solution contains: moles of solute = (0.50 mol/kg) x (1000 g/kg) / 109.94 g/mol = 4.55 mol mass of solvent = 1000 g (since the solution is made with water) molality = 4.55 mol / 1 kg = 4.55 m Finally, we can use the freezing point depression equation to find the expected freezing point (ΔTf): ΔTf = i x Kf x molality where Kf for water is 1.86°C/m and i = 2 (as calculated earlier). ΔTf = 2 x 1.86°C/m x 4.55 m = 16.99°C Since the freezing point depression is the difference between the freezing point of the pure solvent (0°C for water) and the freezing point of the solution, the expected freezing point is: expected freezing point = 0°C - 16.99°C = -16.99°C Rounded to one decimal place, the expected freezing point is -17.0°C, which is closest to answer choice C (-2.8°C after converting from Kelvin to Celsius).

Question 6

Place the following solutions in order of increasing osmotic pressure. I.0.15 M C₂H₆O₂ II.0.15 M SrCl₂ III.0.15 M NaF A) III < I < II B) II < III < I C) I < II < III D) II < I < III E) I < III < II

Accepted Answer

Osmotic pressure depends on the concentration of particles in solution. SrCl2 dissociates into 3 ions, NaF into 2 ions, and C2H6O2 does not dissociate, so the order is I < III < II.

Question 7

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. A) 0.100 m AlCl₃ B) 0.100 m LiBr C) 0.100 m BaCl₂ D) 0.100 m C₆H₁₂O₆ E) They all have the same boiling point.

Accepted Answer

AlCl3 dissociates into four particles (1 Al3+ and 3 Cl-), increasing the boiling point the most due to the highest van't Hoff factor.

Question 8

A solution is prepared by adding 30.00 g of lactose (milk sugar)to 110.0 g of water at 55° The partial pressure of water above the solution is ________ torr.The vapor pressure of pure water at 55°C is 118.0 torr.The molar mass of lactose is 342.3 g/mol.
A) 1.670
B) 94.1
C) 169.4
D) 116.3
E) 92.7

Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law: P_solution = X_solvent * P_pure. First, calculate the moles of lactose (30.00 g / 342.3 g/mol) and water (110.0 g / 18.015 g/mol). Then, find the mole fraction of water (X_solvent). Finally, multiply the mole fraction by the vapor pressure of pure water (118.0 torr) to find the vapor pressure of the solution, which is approximately 116.3 torr.

Question 9

Identify the solute with the lowest van't Hoff factor. A) nonelectrolyte B) KI C) MgSO₄ D) CaCl₂ E) AlCl₃

Accepted Answer

A nonelectrolyte does not dissociate in solution, so it has a van't Hoff factor of 1 (or very close to 1). Therefore, it has the lowest van't Hoff factor compared to the electrolytes listed (KI, MgSO4, CaCl2, AlCl3) which all have higher van't Hoff factors due to their ability to dissociate in solution.

Question 10

Choose the solvent below that would show the greatest boiling point elevation when used to make a 0.10 m nonelectrolyte solution. A) bromobenzene, K_b = 6.20°C/m B) benzene, K_b = 2.53°C/m C) carbon disulfide, K_b = 2.34°C/m D) water, K_b = 0.512°C/m E) methanol, K_b = 0.83°C/m

Accepted Answer

The boiling point elevation is proportional to the molality of the solution and the molal boiling point constant of the solvent, which is unique for each solvent. The greater the value of the molal boiling point constant, the greater the boiling point elevation for a given molality of the solution. Among the given solvents, bromobenzene has the highest value of the molal boiling point constant, which means it will show the greatest boiling point elevation for a 0.10 m solution.

Question 11

Choose the aqueous solution with the lowest vapor pressure.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. A) 0.120 m C₂H₆O₂ B) 0.040 m (NH₄)₂SO₄ C) 0.060 m Li₂CO₃ D) 0.030 m RbC₂H₃O₂ E) They all have the same vapor pressure.

Accepted Answer

The answer of Choose the aqueous solution with the lowest...

Question 12

Choose the aqueous solution below with the highest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. A) 0.200 m Mg(ClO₄)₂ B) 0.200 m Na₃PO₃ C) 0.200 m HOCH₂CH₂OH D) 0.200 m Ba(NO₃)₂ E) These all have the same freezing point.

Accepted Answer

The freezing point depression is directly proportional to the molality of the solution, so the solution with the highest molality will have the highest freezing point. Since all of these solutions have the same molality, we need to consider other properties. Na+ and Mg2+ are both highly charged ions and will experience greater ion-ion interactions and therefore lower freezing points. Ba2+ is larger and will also have lower ion-ion interactions compared to smaller ions like Na+ and Mg2+. HOCH2CH2OH is a polar molecule and will have weaker interactions than any of the ions. Therefore, C (HOCH2CH2OH) will have the highest freezing point.

Question 13

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. A) 0.100 mKNO₂ B) 0.100 m Li₂SO₄ C) 0.200 m C₃H₈O₃ D) 0.060 m Li₃PO₄ E) They all have the same boiling point.

Accepted Answer

The answer of Choose the aqueous solution that has the...

Question 14

An aqueous solution has a normal boiling point of 103.0°C.What is the freezing point of this solution? For water K_b = 0.51°C/m and K_f = 1.86°C/m. A) -0.82°C B) -3.0°C C) -3.6°C D) -11°C

Accepted Answer

The answer of An aqueous solution has a normal boiling...

Question 15

Which of the following solutions will have the lowest freezing point? A) 0.010 m NH₄Cl B) 0.010 m Li₂CO₃ C) 0.035 m CH₃CH₂CH₂OH D) 0.015 m CaI₂

Accepted Answer

The solution with the lowest freezing point is the one that undergoes the greatest ionization, producing the most particles in solution. CaI2 dissociates into three ions (one Ca2+ and two I-), which results in a higher colligative effect (lowering of the freezing point) compared to the other options which do not dissociate into as many particles.

Question 16

Identify the solute with the highest van't Hoff factor. A) nonelectrolyte B) KI C) MgSO₄ D) CaCl₂ E) AlCl₃

Accepted Answer

AlCl3 has the highest van't Hoff factor because it dissociates into four ions (one Al3+ and three Cl-), which is more than the other compounds listed.

Question 17

A solution is prepared by dissolving 7.00 g of glycerin (C₃H₈O₃)in 201 g of ethanol (C₂H₅OH).The freezing point of the solution is ________°C.The freezing point of pure ethanol is -114.6°C at 1 atm.The molal-freezing-point-depression constant (K_f)for ethanol is 1.99°C/m.The molar masses of glycerin and of ethanol are 92.1 g/mol and 46.1 g/mol,respectively. A) -121.3 B) 0.752 C) -107.9 D) -113.8 E) -115.4

Accepted Answer

The freezing point depression ($\Delta T_f$) is calculated using the formula $\Delta T_f = i \cdot K_f \cdot m$, where $i$ is the van't Hoff factor (which is 1 for glycerin, a non-electrolyte), $K_f$ is the molal freezing point depression constant for the solvent (1.99°C/m for ethanol), and $m$ is the molality of the solution. First, calculate the moles of glycerin ($\frac{7.00 \, \text{g}}{92.1 \, \text{g/mol}}$), then calculate the molality ($\frac{\text{moles of solute}}{\text{kg of solvent}}$). Finally, use the $\Delta T_f$ formula to find the change in freezing point and subtract this from the pure solvent's freezing point (-114.6°C) to find the solution's freezing point.

Question 18

What is the freezing point of a solution of 7.15 g MgCl₂ in 100 g of water? K_f for water is 1.86°C/m. A) -0.140°C B) -1.40°C C) -2.80°C D) -4.18°C

Accepted Answer

The answer of What is the freezing point of a...

Question 19

Choose the aqueous solution below with the lowest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. A) 0.075 m LiCl B) 0.075m (NH₄)₃PO₄ C) 0.075 m NaBrO₄ D) 0.075 m KCN E) 0.075 m KNO₂

Accepted Answer

The freezing point depression is proportional to the van't Hoff factor (i), which is the number of particles the solute dissociates into. (NH4)3PO4 dissociates into 4 ions (3 NH4+ and 1 PO4^3-), giving it the highest van't Hoff factor among the options, resulting in the lowest freezing point.

Question 20

The osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C₉H₈O₄)in 0.250 L of water at 25°C is ________ atm. A) 13.6 B) 1.14 × 10^-3 C) 0.0136 D) 2.45 E) 1.38

Accepted Answer

To calculate the osmotic pressure of a solution, we can use the equation:

π = iMRT

Where:
- π = osmotic pressure
- i = van't Hoff factor (the number of particles into which a solute dissociates in solution)
- M = molarity of the solution (moles of solute per liter of solution)
- R = gas constant (0.08206 L·atm/(mol·K))
- T = temperature in kelvin

First, we need to calculate the molarity of the aspirin solution:

molecular weight of aspirin = 180.16 g/mol
25.0 mg of aspirin = 0.025 g

moles of aspirin = 0.025 g / 180.16 g/mol = 1.388 x 10^-4 mol

Molarity = moles of solute / liters of solution
Molarity = 1.388 x 10^-4 mol / 0.250 L = 5.55 x 10^-4 M

Aspirin does not dissociate in water so the van't Hoff factor is 1.

Now we can plug in the values to calculate the osmotic pressure:

π = iMRT
π = (1)(5.55 x 10^-4 M)(0.08206 L·atm/(mol·K))(298 K)
π = 1.36 atm

Therefore, the osmotic pressure of the aspirin solution at 25°C is 1.36 atm, which is closest to choice C (0.0136 atm).

Quiz 13: Solutions

At a given temperature,the vapor pressures of hexane and octane are 183 mm Hg and 59.2 mm Hg,respectively.Calculate the total vapor pressure over a solution of hexane and octane.The mole fraction of hexane (X_hexane) is 0.580.

Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water.The molal-freezing-point-depression constant (K_f) for water is 1.86°C/m.

Calculate the freezing point of a solution of 40.0 g methyl salicylate,C₇H₆O₂,dissolved in 800.g of benzene,C₆H₆.K_f for benzene is 5.10°C/m and the freezing point is 5.50°C for benzene.

Place the following aqueous solutions of nonvolatile,nonionic compounds in order of decreasing osmotic pressure. I.0.011 M ethanol II.0.00095 M fructose III.0.0060 M glycerin

What is the expected freezing point of a 0.50 m solution of Li₂SO₄ in water? K_f for water is 1.86°C/m.

Place the following solutions in order of increasing osmotic pressure. I.0.15 M C₂H₆O₂ II.0.15 M SrCl₂ III.0.15 M NaF

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

A solution is prepared by adding 30.00 g of lactose (milk sugar) to 110.0 g of water at 55° The partial pressure of water above the solution is ________ torr.The vapor pressure of pure water at 55°C is 118.0 torr.The molar mass of lactose is 342.3 g/mol.

Identify the solute with the lowest van't Hoff factor.

Choose the solvent below that would show the greatest boiling point elevation when used to make a 0.10 m nonelectrolyte solution.

Choose the aqueous solution with the lowest vapor pressure.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

Choose the aqueous solution below with the highest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

An aqueous solution has a normal boiling point of 103.0°C.What is the freezing point of this solution? For water K_b = 0.51°C/m and K_f = 1.86°C/m.

Which of the following solutions will have the lowest freezing point?

Identify the solute with the highest van't Hoff factor.

What is the freezing point of a solution of 7.15 g MgCl₂ in 100 g of water? K_f for water is 1.86°C/m.

Choose the aqueous solution below with the lowest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

The osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C₉H₈O₄) in 0.250 L of water at 25°C is ________ atm.

Quiz 13: Solutions

At a given temperature,the vapor pressures of hexane and octane are 183 mm Hg and 59.2 mm Hg,respectively.Calculate the total vapor pressure over a solution of hexane and octane.The mole fraction of hexane (Xhexane) is 0.580.

Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water.The molal-freezing-point-depression constant (Kf) for water is 1.86°C/m.

Calculate the freezing point of a solution of 40.0 g methyl salicylate,C7H6O2,dissolved in 800.g of benzene,C6H6.Kf for benzene is 5.10°C/m and the freezing point is 5.50°C for benzene.

Place the following aqueous solutions of nonvolatile,nonionic compounds in order of decreasing osmotic pressure. I.0.011 M ethanol II.0.00095 M fructose III.0.0060 M glycerin

What is the expected freezing point of a 0.50 m solution of Li2SO4 in water? Kf for water is 1.86°C/m.

Place the following solutions in order of increasing osmotic pressure. I.0.15 M C2H6O2 II.0.15 M SrCl2 III.0.15 M NaF

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

A solution is prepared by adding 30.00 g of lactose (milk sugar) to 110.0 g of water at 55° The partial pressure of water above the solution is ________ torr.The vapor pressure of pure water at 55°C is 118.0 torr.The molar mass of lactose is 342.3 g/mol.

Identify the solute with the lowest van't Hoff factor.

Choose the solvent below that would show the greatest boiling point elevation when used to make a 0.10 m nonelectrolyte solution.

Choose the aqueous solution with the lowest vapor pressure.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

Choose the aqueous solution below with the highest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

Choose the aqueous solution that has the highest boiling point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

An aqueous solution has a normal boiling point of 103.0°C.What is the freezing point of this solution? For water Kb = 0.51°C/m and Kf = 1.86°C/m.

Which of the following solutions will have the lowest freezing point?

Identify the solute with the highest van't Hoff factor.

What is the freezing point of a solution of 7.15 g MgCl2 in 100 g of water? Kf for water is 1.86°C/m.

Choose the aqueous solution below with the lowest freezing point.These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.

The osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C9H8O4) in 0.250 L of water at 25°C is ________ atm.

At a given temperature,the vapor pressures of hexane and octane are 183 mm Hg and 59.2 mm Hg,respectively.Calculate the total vapor pressure over a solution of hexane and octane.The mole fraction of hexane (X_hexane) is 0.580.

Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 grams of water.The molal-freezing-point-depression constant (K_f) for water is 1.86°C/m.

Calculate the freezing point of a solution of 40.0 g methyl salicylate,C₇H₆O₂,dissolved in 800.g of benzene,C₆H₆.K_f for benzene is 5.10°C/m and the freezing point is 5.50°C for benzene.

What is the expected freezing point of a 0.50 m solution of Li₂SO₄ in water? K_f for water is 1.86°C/m.

Place the following solutions in order of increasing osmotic pressure. I.0.15 M C₂H₆O₂ II.0.15 M SrCl₂ III.0.15 M NaF

An aqueous solution has a normal boiling point of 103.0°C.What is the freezing point of this solution? For water K_b = 0.51°C/m and K_f = 1.86°C/m.

What is the freezing point of a solution of 7.15 g MgCl₂ in 100 g of water? K_f for water is 1.86°C/m.

The osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C₉H₈O₄) in 0.250 L of water at 25°C is ________ atm.