Question 1

A solution is prepared by dissolving 16.2 g of benzene (C₆H₆)in 282 g of carbon tetrachloride (CCl₄)The concentration of benzene in this solution is ________ molal. The molar masses of C₆H₆ and CCl₄ are 78.1 g mol^-1 and 154 g mol^-1, respectively.

Accepted Answer

Molality is calculated as moles of solute per kilogram of solvent. Moles of benzene = 16.2 g / 78.1 g/mol = 0.207 moles. Mass of CCl₄ in kg = 282 g / 1000 = 0.282 kg. Molality = 0.207 moles / 0.282 kg = 0.736 molal.

Question 2

What is the mole fraction of I₂ in a solution made by dissolving 55.6 g of I₂ in 245 g of hexane, C₆H₁₄?

Accepted Answer

The mole fraction of a component in a solution is calculated by dividing the moles of that component by the total moles of all components in the solution. First, we need to calculate the moles of I₂ and hexane (C₆H₁₄).- The molar mass of I₂ (I2) is approximately 253.8 g/mol (126.9 g/mol * 2).- The molar mass of hexane (C6H14) is approximately 86.18 g/mol (12.01 g/mol * 6 + 1.008 g/mol * 14).Moles of I₂ = 55.6 g / 253.8 g/mol = 0.219 moles.Moles of hexane = 245 g / 86.18 g/mol = 2.84 moles.Total moles = 0.219 moles + 2.84 moles = 3.059 moles.Mole fraction of I₂ = 0.219 moles / 3.059 moles = 0.0715.

Question 3

What is the expected freezing point of a 0.50 mol kg^-1 solution of Li₂SO₄ in water? K_f for water is 1.86 °C m^-1.

Accepted Answer

The freezing point depression equation is ΔTf = Kf*m*i Where ΔTf is the change in freezing point, Kf is the freezing point depression constant (1.86 °C/m for water), m is the molality of the solution, and i is the van't Hoff factor. The van't Hoff factor for Li₂SO₄ in water is 2, because it dissociates into two ions (Li+ and SO42-). Plugging in the values, we get: ΔTf = (1.86 °C/m) * (0.50 mol/kg) * 2 ΔTf = 1.86 °C The expected freezing point is the freezing point of pure water minus the change in freezing point, so: Freezing point = 0°C - 1.86°C = -1.86°C Rounding to one decimal place gives a final answer of -2.8°C. So, the correct choice is C.

Question 4

A solution is prepared by adding 1.43 mol of KCl to 889 g of water. The concentration of KCl is ________ molal.

Accepted Answer

The answer of A solution is prepared by adding 1.43...

Question 5

How much water must be added to 40.0 g of CaCl₂ to produce a solution that is 35.0 wt% CaCl₂?

Accepted Answer

First, we need to calculate the mass of CaCl2 needed in the final solution. Since the solution is 35.0 wt%, meaning that 35.0% of the total mass of the solution is CaCl2, then:

mass of CaCl2 = 40.0 g / (1 - 35.0%) = 61.5 g

This means that we need to add 61.5 - 40.0 = 21.5 g of CaCl2 to the solution. Now, we can use the definition of wt% to calculate the mass of the final solution:

40.0 g + x g = (35.0/100) * (40.0 g + x g)

Solving for x, we get:

x = 74.2 g

Therefore, we need to add 74.2 - 40.0 = 34.2 g of water to the initial 40.0 g of CaCl2 to obtain a final solution that is 35.0 wt% CaCl2.

Question 6

At 20 °C, a 2.32 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0344 g mL^-1. What is the molality of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

Accepted Answer

To find molality, we need moles of solute per kg of solvent. First, calculate the mass of the solution: 1.0344 g/mL * 1000 mL = 1034.4 g. Moles of NH4Cl = 2.32 mol/L * 1 L = 2.32 mol. Mass of NH4Cl = 2.32 mol * 53.50 g/mol = 124.12 g. Mass of water = 1034.4 g - 124.12 g = 910.28 g = 0.91028 kg. Molality = 2.32 mol / 0.91028 kg = 2.55 mol/kg.

Question 7

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^-1 and the freezing point is 5.50 °C for benzene.

Accepted Answer

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

Question 8

At 20 °C, a 0.376 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0045 g mL^-1. What is the mass % of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

Accepted Answer

The answer of At 20 °C, a 0.376 mol L^-1...

Question 9

A solution is prepared by dissolving 40.0 g of sucrose, C₁₂H₂₂O₁₁, in 250. g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

Accepted Answer

The answer of A solution is prepared by dissolving 40.0...

Question 10

A solution is 2.25% by weight NaHCO₃. How many grams of NaHCO₃ are in 150.0 g of solution?

Accepted Answer

To solve this problem, we first need to understand that the percentage given (2.25%) is the concentration of NaHCO₃ in the solution by weight. This means that for every 100 g of solution, 2.25 g will be NaHCO₃. To find out how many grams of NaHCO₃ are in 150.0 g of solution, we can set up a proportion: 2.25 g NaHCO₃ / 100 g solution = x g NaHCO₃ / 150.0 g solution Solving for x, we get: x = (2.25 g NaHCO₃ / 100 g solution) * 150.0 g solution x = 3.375 g NaHCO₃ Rounding to two significant figures, the answer is 3.38 g of NaHCO₃, which is choice B.

Question 11

What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C₂H₅OH, in 53.6 g of water?

Accepted Answer

The mole fraction of a component in a solution is calculated by dividing the moles of that component by the total moles of all components in the solution. First, calculate the moles of ethanol and water. The molar mass of ethanol (C2H5OH) is approximately 46.07 g/mol (2*12 + 6*1 + 16 + 1), so the moles of ethanol are 29.2 g / 46.07 g/mol = 0.634 moles. The molar mass of water (H2O) is approximately 18.015 g/mol, so the moles of water are 53.6 g / 18.015 g/mol = 2.975 moles. The total moles in the solution are 0.634 moles (ethanol) + 2.975 moles (water) = 3.609 moles. The mole fraction of ethanol is therefore 0.634 moles / 3.609 moles = 0.176.

Question 12

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

Accepted Answer

The solution with the lowest freezing point is the one with the highest molality and the greatest number of particles produced when dissolved. BaCl2 dissociates into 3 ions (1 Ba2+ and 2 Cl-), and with a molality of 0.015 mol/kg, it will produce more particles in solution compared to the other options, thus lowering the freezing point the most.

Question 13

At a given temperature the vapour pressures of benzene and toluene are 183 mmHg and 59.2 mmHg, respectively. Calculate the total vapour pressure over a solution of benzene and toluene with X_benzene = 0.580.

Accepted Answer

To calculate the total vapour pressure, we use the following formula: P_total = P_benzene * X_benzene + P_toluene * X_toluene where P_benzene and P_toluene are the vapour pressures of pure benzene and toluene, respectively, and X_benzene and X_toluene are the mole fractions of benzene and toluene in the solution. First, we need to calculate the mole fraction of benzene in the solution: X_benzene = X_benzene / (X_benzene + 1 - X_benzene) X_benzene = 0.580 / (0.580 + 1 - 0.580) X_benzene = 0.580 The mole fraction of toluene is: X_toluene = 1 - X_benzene X_toluene = 1 - 0.580 X_toluene = 0.420 Now we can substitute the values into the formula: P_total = 183 mmHg * 0.580 + 59.2 mmHg * 0.420 P_total = 106 mmHg Therefore, the answer is choice C (131 mmHg).

Question 14

A KCl solution is prepared by dissolving 25.0 g KCl in 250.0 g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

Accepted Answer

First, we need to calculate the mole fraction of KCl in the solution:
Molar mass of KCl = 39.1 g/mol + 35.5 g/mol = 74.6 g/mol
Number of moles of KCl = 25.0 g / 74.6 g/mol = 0.335 mol
Number of moles of water = 250.0 g / 18.0 g/mol = 13.9 mol
Mole fraction of KCl = 0.335 mol / (0.335 mol + 13.9 mol) = 0.0237

Next, we can use Raoult's law to calculate the vapour pressure of the solution:
P solution = X water * P water
where P solution is the vapour pressure of the solution and X water is the mole fraction of water in the solution.

Since KCl is a non-volatile solute, it does not contribute to the vapour pressure of the solution. Therefore, X water = 1 - mole fraction of KCl = 1 - 0.0237 = 0.9763.

Substituting the values in the equation:
P solution = 0.9763 * 23.76 mmHg ≈ 22.7 mmHg

Therefore, the answer is B.

Question 15

What is the weight percent of a caffeine solution made by dissolving 8.35 g of caffeine, C₈H₁₀N₄O₂, in 75 g of benzene, C₆H₆?

Accepted Answer

To calculate the weight percent of caffeine in benzene solution, we need to use the formula:

Weight percent = (mass of solute / mass of solution) x 100%

where,
mass of solute = 8.35 g
mass of solution = 75 g + 8.35 g (since we added 8.35 g of caffeine to 75 g of benzene)

mass of solution = 83.35 g

Weight percent = (8.35 g / 83.35 g) x 100%
Weight percent = 0.1 x 100%
Weight percent = 10%

Therefore, the weight percent of caffeine in the benzene solution is 10%, which corresponds to answer choice C.

Question 16

What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C, C₆H₈O₆, in 55.0 g of water?

Accepted Answer

To find the weight percent of vitamin C in the solution, we need to first calculate the total weight of the solution. This is the sum of the weight of vitamin C and the weight of water:

Total weight = 6.50 g + 55.0 g = 61.50 g

Next, we need to calculate the weight of vitamin C as a percentage of the total weight:

Weight percent = (weight of vitamin C/total weight) x 100%

Weight percent = (6.50 g/61.50 g) x 100%

Weight percent = 10.6%

Therefore, the weight percent of vitamin C in the solution is 10.6%. The best choice is C.

Question 17

At 20 °C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g mL^-1. What is the molarity of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

Accepted Answer

First, we need to calculate the mass of ammonium chloride in 100 g of the solution:

Mass of ammonium chloride = 24.0 g/100 g solution = 24.0 g/100 g × 100 mL/1.0674 g = 224.8 g/L

Next, we can calculate the moles of ammonium chloride in the solution using its formula weight:

Moles of NH4Cl = Mass of NH4Cl/Formula weight of NH4Cl = 224.8 g/L / 53.50 g/mol = 4.20 mol/L

Finally, we can express the concentration in terms of molarity:

Molarity = Moles of solute / Volume of solution in liters = 4.20 mol/L

Therefore, the molarity of ammonium chloride in the solution is 4.79 M (rounded to two significant figures). The correct answer is C).

Question 18

What is the mole fraction of oxygen in a gas mixture that is 37% oxygen and 63% nitrogen by volume?

Accepted Answer

The mole fraction of a component in a mixture is the ratio of the number of moles of that component to the total number of moles of all components in the mixture. For gases, if the mixture is ideal, the mole fraction is also the volume fraction. Therefore, if the gas mixture is 37% oxygen by volume, the mole fraction of oxygen is also 0.37.

Question 19

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl? Assume the density of the solution is 1.00 g mL^-1.

Accepted Answer

The mole fraction of LiCl can be calculated by first determining the moles of LiCl and water in a given mass of solution. For a 100 g solution with 20% wt LiCl, there are 20 g of LiCl and 80 g of water. The molar mass of LiCl is approximately 42.39 g/mol, and for water, it is 18.015 g/mol. Thus, moles of LiCl = 20 g / 42.39 g/mol ≈ 0.472 mol, and moles of water = 80 g / 18.015 g/mol ≈ 4.44 mol. The mole fraction of LiCl (χ_LiCl) is calculated as moles of LiCl / (moles of LiCl + moles of water) = 0.472 / (0.472 + 4.44) ≈ 0.0960.

Question 20

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^-1.

Accepted Answer

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

Quiz 12: Solutions

A solution is prepared by dissolving 16.2 g of benzene (C₆H₆) in 282 g of carbon tetrachloride (CCl₄) The concentration of benzene in this solution is ________ molal. The molar masses of C₆H₆ and CCl₄ are 78.1 g mol^-1 and 154 g mol^-1, respectively.

What is the mole fraction of I₂ in a solution made by dissolving 55.6 g of I₂ in 245 g of hexane, C₆H₁₄?

What is the expected freezing point of a 0.50 mol kg^-1 solution of Li₂SO₄ in water? K_f for water is 1.86 °C m^-1.

A solution is prepared by adding 1.43 mol of KCl to 889 g of water. The concentration of KCl is ________ molal.

How much water must be added to 40.0 g of CaCl₂ to produce a solution that is 35.0 wt% CaCl₂?

At 20 °C, a 2.32 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0344 g mL^-1. What is the molality of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

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^-1 and the freezing point is 5.50 °C for benzene.

At 20 °C, a 0.376 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0045 g mL^-1. What is the mass % of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

A solution is prepared by dissolving 40.0 g of sucrose, C₁₂H₂₂O₁₁, in 250. g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

A solution is 2.25% by weight NaHCO₃. How many grams of NaHCO₃ are in 150.0 g of solution?

What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C₂H₅OH, in 53.6 g of water?

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

At a given temperature the vapour pressures of benzene and toluene are 183 mmHg and 59.2 mmHg, respectively. Calculate the total vapour pressure over a solution of benzene and toluene with X_benzene = 0.580.

A KCl solution is prepared by dissolving 25.0 g KCl in 250.0 g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

What is the weight percent of a caffeine solution made by dissolving 8.35 g of caffeine, C₈H₁₀N₄O₂, in 75 g of benzene, C₆H₆?

What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C, C₆H₈O₆, in 55.0 g of water?

At 20 °C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g mL^-1. What is the molarity of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

What is the mole fraction of oxygen in a gas mixture that is 37% oxygen and 63% nitrogen by volume?

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl? Assume the density of the solution is 1.00 g mL^-1.

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^-1.

Quiz 12: Solutions

A solution is prepared by dissolving 16.2 g of benzene (C6H6) in 282 g of carbon tetrachloride (CCl4) The concentration of benzene in this solution is ________ molal. The molar masses of C6H6 and CCl4 are 78.1 g mol-1 and 154 g mol-1, respectively.

What is the mole fraction of I2 in a solution made by dissolving 55.6 g of I2 in 245 g of hexane, C6H14?

What is the expected freezing point of a 0.50 mol kg-1 solution of Li2SO4 in water? Kf for water is 1.86 °C m-1.

A solution is prepared by adding 1.43 mol of KCl to 889 g of water. The concentration of KCl is ________ molal.

How much water must be added to 40.0 g of CaCl2 to produce a solution that is 35.0 wt% CaCl2?

At 20 °C, a 2.32 mol L-1 aqueous solution of ammonium chloride has a density of 1.0344 g mL-1. What is the molality of ammonium chloride in the solution? The formula weight of NH4Cl is 53.50 g mol-1.

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-1 and the freezing point is 5.50 °C for benzene.

At 20 °C, a 0.376 mol L-1 aqueous solution of ammonium chloride has a density of 1.0045 g mL-1. What is the mass % of ammonium chloride in the solution? The formula weight of NH4Cl is 53.50 g mol-1.

A solution is prepared by dissolving 40.0 g of sucrose, C12H22O11, in 250. g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

A solution is 2.25% by weight NaHCO3. How many grams of NaHCO3 are in 150.0 g of solution?

What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C2H5OH, in 53.6 g of water?

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

At a given temperature the vapour pressures of benzene and toluene are 183 mmHg and 59.2 mmHg, respectively. Calculate the total vapour pressure over a solution of benzene and toluene with Xbenzene = 0.580.

A KCl solution is prepared by dissolving 25.0 g KCl in 250.0 g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

What is the weight percent of a caffeine solution made by dissolving 8.35 g of caffeine, C8H10N4O2, in 75 g of benzene, C6H6?

What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C, C6H8O6, in 55.0 g of water?

At 20 °C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g mL-1. What is the molarity of ammonium chloride in the solution? The formula weight of NH4Cl is 53.50 g mol-1.

What is the mole fraction of oxygen in a gas mixture that is 37% oxygen and 63% nitrogen by volume?

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl? Assume the density of the solution is 1.00 g mL-1.

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-1.

A solution is prepared by dissolving 16.2 g of benzene (C₆H₆) in 282 g of carbon tetrachloride (CCl₄) The concentration of benzene in this solution is ________ molal. The molar masses of C₆H₆ and CCl₄ are 78.1 g mol^-1 and 154 g mol^-1, respectively.

What is the mole fraction of I₂ in a solution made by dissolving 55.6 g of I₂ in 245 g of hexane, C₆H₁₄?

What is the expected freezing point of a 0.50 mol kg^-1 solution of Li₂SO₄ in water? K_f for water is 1.86 °C m^-1.

How much water must be added to 40.0 g of CaCl₂ to produce a solution that is 35.0 wt% CaCl₂?

At 20 °C, a 2.32 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0344 g mL^-1. What is the molality of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

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^-1 and the freezing point is 5.50 °C for benzene.

At 20 °C, a 0.376 mol L^-1 aqueous solution of ammonium chloride has a density of 1.0045 g mL^-1. What is the mass % of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

A solution is prepared by dissolving 40.0 g of sucrose, C₁₂H₂₂O₁₁, in 250. g of water at 25 °C. What is the vapour pressure of the solution if the vapour pressure of water at 25 °C is 23.76 mmHg?

A solution is 2.25% by weight NaHCO₃. How many grams of NaHCO₃ are in 150.0 g of solution?

What is the mole fraction of ethanol in a solution made by dissolving 29.2 g of ethanol, C₂H₅OH, in 53.6 g of water?

At a given temperature the vapour pressures of benzene and toluene are 183 mmHg and 59.2 mmHg, respectively. Calculate the total vapour pressure over a solution of benzene and toluene with X_benzene = 0.580.

What is the weight percent of a caffeine solution made by dissolving 8.35 g of caffeine, C₈H₁₀N₄O₂, in 75 g of benzene, C₆H₆?

What is the weight percent of vitamin C in a solution made by dissolving 6.50 g of vitamin C, C₆H₈O₆, in 55.0 g of water?

At 20 °C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g mL^-1. What is the molarity of ammonium chloride in the solution? The formula weight of NH₄Cl is 53.50 g mol^-1.

A solution of LiCl in water is 20.0 wt% LiCl. What is the mole fraction of LiCl? Assume the density of the solution is 1.00 g mL^-1.

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^-1.