Question 1

For each of the following solutions,describe the deviation with respect to Raoult's Law. -hexane (C₆H₁₄)and octane (C₈H₁₈) A)relatively ideal B)positive deviation C)negative deviation D)more information needed E)none of these

Accepted Answer

Hexane and octane are both nonpolar hydrocarbons with similar molecular sizes and structures, leading to similar intermolecular forces between them. This similarity results in a mixture that behaves relatively ideally, closely following Raoult's Law.

Question 2

Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr.
-What is the mole fraction of benzene in a benzene-toluene solution whose vapor pressure is 51 torr at 20°C?
A)0.26
B)0.45
C)0.55
D)0.67
E)0.74

Accepted Answer

According to Raoult's law, the vapor pressure of a solution is equal to the mole fraction of each component multiplied by its vapor pressure in its pure state.

Let x be the mole fraction of benzene. Then, the mole fraction of toluene is (1-x).

Using the given vapor pressures, we can set up the following equation:

51 = x(76) + (1-x)(21)

Solving for x gives x = 0.55. Therefore, the mole fraction of benzene in the solution is 0.55.

Thus, the best choice is C.

Question 3

Liquid A and liquid B form a solution that behaves ideally according to Raoult's law.The vapor pressures of the pure substances A and B are 233 torr and 135 torr,respectively.Determine the vapor pressure over the solution if 1.21 moles of liquid A is added to 5.30 moles of liquid B.
A)153 torr
B)188 torr
C)215 torr
D)760 torr
E)43.3 torr

Accepted Answer

The vapor pressure of an ideal solution can be calculated using Raoult's law, which states that the vapor pressure of a solution is the sum of the vapor pressures of each component multiplied by its mole fraction in the solution. First, calculate the mole fractions of A and B:- Total moles = moles of A + moles of B = 1.21 + 5.30 = 6.51 moles- Mole fraction of A (X_A) = moles of A / total moles = 1.21 / 6.51- Mole fraction of B (X_B) = moles of B / total moles = 5.30 / 6.51Then, apply Raoult's law to find the total vapor pressure (P_total):- P_total = (X_A * P_A) + (X_B * P_B)- P_total = (1.21 / 6.51 * 233) + (5.30 / 6.51 * 135)Calculating the values:- P_total ≈ (0.186 * 233) + (0.814 * 135) ≈ 43.3 + 109.9 ≈ 153 torrTherefore, the vapor pressure over the solution is approximately 153 torr.

Question 4

Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr.
-If the mole fraction of benzene in a particular benzene-toluene solution is 0.64,what is the mole fraction of benzene in the vapor phase in equilibrium with that solution?
A)0.24
B)0.50
C)0.64
D)0.78
E)0.87

Accepted Answer

The answer of Solutions of benzene and toluene obey Raoult's...

Question 5

Benzene and toluene form an ideal solution.At 298 K,what is the mole fraction of benzene in the liquid that is in equilibrium with a vapor that has equal partial pressures of benzene and toluene? At 298 K,the vapor pressures of pure benzene and pure toluene are 95 and 28 torr,respectively.
A)0.50
B)0.77
C)0.23
D)0.30
E)none of these

Accepted Answer

The answer of Benzene and toluene form an ideal solution.At...

Question 6

A solution contains 1 mole of liquid A and 3 moles of liquid B.This solution has a vapor pressure of 314 torr at 25°C.At 25°C,liquid A has a vapor pressure of 265 torr and liquid B has a vapor pressure of 355 torr.Which of the following is true?
A)This solution exhibits a positive deviation from Raoult's Law.
B)This solution exhibits a negative deviation from Raoult's Law.
C)This solution is ideal.
D)More information is needed to answer this question.
E)None of these (A-D).

Accepted Answer

The observed vapor pressure of the solution (314 torr) is less than the vapor pressure predicted by Raoult's Law (which would be 1 x 265 torr + 3 x 355 torr = 1340 torr). This indicates a positive deviation from Raoult's Law, which occurs when the intermolecular forces between the components of the mixture are weaker than the forces between like molecules. This allows for more molecules to escape into the gas phase than predicted by Raoult's Law, resulting in a lower observed vapor pressure.

Question 7

Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr.
-A benzene-toluene solution is allowed to come to equilibrium with its vapor.The vapor is then condensed and found to contain 50.0 mole percent of each component.Calculate the composition (mole percent)of the original solution.The vapor pressures of pure benzene and toluene at this temperature are: 750.torr and 300.torr,respectively.
A)50.2% benzene
B)28.6% benzene
C)71.0% benzene
D)40.0% benzene
E)none of these

Accepted Answer

Let x be the mole fraction of benzene in the original solution.
According to Raoult's law, the vapor pressure of the solution is:
P = x*76 + (1-x)*21
In equilibrium, the vapor should have the same composition as the solution:
0.5 = P_benzene/P = x*76/P + (1-x)*21/P
0.5*P = x*76 + (1-x)*21
Substitute P = 750 torr and solve for x:
375 = 55x + 21 - 21x
354 = 34x
x = 10.4
Therefore, the original solution had a mole fraction of benzene of 10.4/100 = 0.104, or 10.4 mole percent.
The composition in mole percent is 10.4% benzene and 89.6% toluene.
The best choice is B.

Question 8

A solution of two liquids,A and B,shows negative deviation from Raoult's law.This means that:
A)The molecules of A interact strongly with other A-type molecules.
B)The two liquids have a positive heat of solution.
C)Molecules of A interact weakly,if at all,with B molecules.
D)The molecules of A hinder the strong interaction between B molecules.
E)Molecules of A interact more strongly with B than A with A,or B with B.

Accepted Answer

Negative deviation from Raoult's law indicates that the interactions between the different molecules in the solution (A and B) are stronger than the interactions among the molecules of each liquid separately. This leads to a lower vapor pressure than predicted by Raoult's law, which is consistent with choice E.

Question 9

A solution is prepared from 53.8 g of a nonvolatile,nondissociating solute and 85.0 g of water.The vapor pressure of the solution at 60°C is 132 torr.The vapor pressure of water at 60°C is 150.torr.What is the molar mass of the solute?
A)61.1 g/mol
B)11.4 g/mol
C)34.6 g/mol
D)186 g/mol
E)83.6 g/mol

Accepted Answer

The vapor pressure lowering can be used to find the mole fraction of the solute, which can then be used to calculate the molar mass. Using Raoult's Law: P_solution = X_solvent * P_solvent. The mole fraction of the solvent (water) is 132/150. Using the mole fraction and the mass of water, the molar mass of the solute is calculated to be approximately 83.6 g/mol.

Question 10

For each of the following solutions,describe the deviation with respect to Raoult's Law. -acetone (C₃H₆O)and water A)relatively ideal B)positive deviation C)negative deviation D)more information needed E)none of these

Accepted Answer

Negative deviation occurs when the intermolecular forces between the components of the solution are stronger than the intermolecular forces between the pure components. This results in a decrease in the vapor pressure of the solution compared to what would be predicted by Raoult's Law. Acetone and water form hydrogen bonds with each other, which results in a negative deviation from Raoult's Law.

Question 11

At a given temperature,you have a mixture of benzene (vapor pressure of pure benzene = 745 torr)and toluene (vapor pressure of pure toluene = 290.torr).The mole fraction of benzene in the solution is 0.590.Assuming ideal behavior,calculate the mole fraction of toluene in the vapor above the solution.
A)0.213
B)0.778
C)0.641
D)0.359
E)0.590

Accepted Answer

Raoult's law states that the partial pressure of a component in a mixture is equal to the product of its mole fraction and the vapor pressure of the pure component. For benzene, the partial pressure is:Pbenzene = Xbenzene * Pbenzene^0 = 0.590 * 745 torr = 439.55 torrFor toluene, the partial pressure is:Ptoluene = Xtoluene * Ptoluene^0 = (1 - Xbenzene) * 290 torr = 0.410 * 290 torr = 120.90 torrThe mole fraction of toluene in the vapor is:Xtoluene = Ptoluene / Ptotal = 120.90 torr / (439.55 torr + 120.90 torr) = 0.213

Question 12

For each of the following solutions,describe the deviation with respect to Raoult's Law. -hexane (C₆H₁₄)and chloroform (CHCl₃) A)relatively ideal B)positive deviation C)negative deviation D)more information needed E)none of these

Accepted Answer

Hexane and chloroform form a mixture that shows a positive deviation from Raoult's Law. This means that the vapor pressure of the mixture is higher than expected based on the vapor pressure of the individual components, indicating a stronger intermolecular interaction between the two molecules.

Question 13

At 40°C,heptane has a vapor pressure of about 92.2 torr and octane has a vapor pressure of about 31.2 torr.Assuming ideal behavior,what is the vapor pressure of a solution that contains twice as many moles of heptane as octane?
A)61.5 torr
B)51.5 torr
C)71.9 torr
D)82.3 torr
E)none of these

Accepted Answer

According to Raoult's law, the vapor pressure of a solution is equal to the mole fraction of the component multiplied by its vapor pressure in the pure state. Let x be the mole fraction of octane, then the mole fraction of heptane is 2x because there are twice as many moles of heptane. Therefore:

x(31.2 torr) + 2x(92.2 torr) = (31.2 + 184.4)x torr
= 215.6x torr

The total mole fraction of the solution is x + 2x = 3x. Therefore, the vapor pressure of the solution is:

(Vapor pressure of octane) + (Vapor pressure of heptane)
= 31.2x + 184.4x = 215.6x

Dividing both sides by 3x, we get:

Vapor pressure of the solution = 215.6/3 torr = 71.9 torr

Therefore, the answer is C.

Question 14

A liquid-liquid solution is called an ideal solution if:
I.It obeys PV = nRT.
II.It obeys Raoult's law.
III.Solute-solute,solvent-solvent,and solute-solvent interactions are very similar.
IV.Solute-solute,solvent-solvent,and solute-solvent interactions are quite different.
A)I,II,III
B)I,II,IV
C)II,III
D)II,IV
E)I,III,IV

Accepted Answer

An ideal solution is defined as one where the solute-solute, solvent-solvent, and solute-solvent interactions are very similar. Therefore, statement III is correct. Raoult's law states that the partial vapor pressure of each component in a mixture of liquids is directly proportional to its mole fraction in the mixture. An ideal solution follows Raoult's law, so statement II is also correct. However, an ideal solution does not necessarily have to follow the ideal gas law (statement I), nor do the interactions have to be quite different (statement IV).

Question 15

A salt solution sits in an open beaker.Assuming constant temperature and pressure,the vapor pressure of the solution
A)increases over time
B)decreases over time
C)stays the same over time
D)need to know which salt is in the solution to answer this
E)need to know the temperature and pressure to answer this

Accepted Answer

The presence of a solute (salt) lowers the vapor pressure of the solution compared to that of the pure solvent. However, since the beaker is open, some of the solvent molecules will still be able to escape and evaporate into the surrounding atmosphere. Therefore, over time, the concentration of salt in the solution will increase and the vapor pressure will decrease, leading to choice B.

Question 16

A solution of CH₃OH in H₂O would most likely A)be ideal B)show positive deviations from Raoult's law C)show negative deviations from Raoult's law D)not be ideal,but the deviations cannot be predicted E)obey Raoult's law

Accepted Answer

The solution of CH₃OH in H₂O would most likely show negative deviations from Raoult's law because the presence of the highly polar CH₃OH molecule would cause a reduction in the vapor pressure of H₂O, leading to a decrease in the overall vapor pressure of the solution. This would result in a lower mole fraction of each component in the vapor phase compared to what would be expected if Raoult's law were obeyed, indicating negative deviations from Raoult's law.

Question 17

At a given temperature,you have a mixture of benzene (vapor pressure of pure benzene = 745 torr)and toluene (vapor pressure of pure toluene = 290 torr).The mole fraction of benzene in the vapor above the solution is 0.590.Assuming ideal behavior,calculate the mole fraction of toluene in the solution.
A)0.213
B)0.778
C)0.641
D)0.359
E)0.590

Accepted Answer

Using Raoult's law, 
P(total) = P(benzene) x mole fraction of benzene + P(toluene) x mole fraction of toluene

We have P(benzene) = 745 torr, mole fraction of benzene = 0.590, and P(toluene) = 290 torr

Therefore, 
P(total) = 745 torr x 0.590 + 290 torr x mole fraction of toluene

Solving for mole fraction of toluene:

290 torr x mole fraction of toluene = P(total) - 745 torr x 0.590 
mole fraction of toluene = (P(total) - 745 torr x 0.590) / 290 torr

Substituting P(total) = 745 torr + 290 torr = 1035 torr, we get

mole fraction of toluene = (1035 torr - 745 torr x 0.590) / 290 torr = 0.641

Therefore, the mole fraction of toluene in the solution is 0.641.

Question 18

A solution is made by adding 0.100 mole of ethyl ether to 0.491 mole of ethyl alcohol.If the vapor pressure of ethyl ether and ethyl alcohol at 20°C are 375 torr and 20.0 torr,respectively,the vapor pressure of the solution at 20°C (assuming ideal behavior)is:
A)80.1 torr
B)315 torr
C)46.8 torr
D)395 torr
E)none of these

Accepted Answer

Raoult's law: P(total) = P(ether) + P(alcohol) = X(ether) * P(ether)^o + X(alcohol) * P(alcohol)^o                                                                 = 0.100/0.591 * 375 torr + 0.491/0.591 * 20.0 torr                                                                 = 80.1 torr

Question 19

Two liquids form a solution and release a quantity of heat.How does the pressure above the solution compare to that predicted by Raoult's law?
A)It will be greater.
B)It will be less.
C)It will be the same.
D)It will show positive deviation.
E)None of these.

Accepted Answer

When two liquids form a solution and release heat, it indicates an exothermic process where the intermolecular forces between the molecules of the mixed liquids are stronger than those in the separate liquids. According to Raoult's law, the partial vapor pressure of each component in a solution is directly proportional to its mole fraction. In this case, because the molecules in the solution are more strongly attracted to each other than to their separate components, they are less likely to escape into the vapor phase. This results in a vapor pressure that is lower than what Raoult's law would predict for an ideal solution, where the intermolecular forces before and after mixing are assumed to be unchanged.

Question 20

An ideal solution is formed from a mixture of the nonvolatile solute urea,CO(NH₂)₂,and methanol,CH₃OH.The vapor pressure of pure methanol at 20°C is 89 mmHg.If 4.4 g of urea is mixed with 39.9 g of methanol,calculate the vapor pressure of the methanol solution. A)4.9 mmHg B)80 mmHg C)74 mmHg D)15 mmHg E)84 mmHg

Accepted Answer

The answer of An ideal solution is formed from a...

Quiz 11: Properties of Solutions

For each of the following solutions,describe the deviation with respect to Raoult's Law. -hexane (C₆H₁₄) and octane (C₈H₁₈)

Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr. -What is the mole fraction of benzene in a benzene-toluene solution whose vapor pressure is 51 torr at 20°C?

Liquid A and liquid B form a solution that behaves ideally according to Raoult's law.The vapor pressures of the pure substances A and B are 233 torr and 135 torr,respectively.Determine the vapor pressure over the solution if 1.21 moles of liquid A is added to 5.30 moles of liquid B.

Solutions of benzene and toluene obey Raoult's law.The vapor pressures at 20°C are: benzene,76 torr;toluene,21 torr. -If the mole fraction of benzene in a particular benzene-toluene solution is 0.64,what is the mole fraction of benzene in the vapor phase in equilibrium with that solution?

Benzene and toluene form an ideal solution.At 298 K,what is the mole fraction of benzene in the liquid that is in equilibrium with a vapor that has equal partial pressures of benzene and toluene? At 298 K,the vapor pressures of pure benzene and pure toluene are 95 and 28 torr,respectively.

A solution contains 1 mole of liquid A and 3 moles of liquid B.This solution has a vapor pressure of 314 torr at 25°C.At 25°C,liquid A has a vapor pressure of 265 torr and liquid B has a vapor pressure of 355 torr.Which of the following is true?

A solution of two liquids,A and B,shows negative deviation from Raoult's law.This means that:

A solution is prepared from 53.8 g of a nonvolatile,nondissociating solute and 85.0 g of water.The vapor pressure of the solution at 60°C is 132 torr.The vapor pressure of water at 60°C is 150.torr.What is the molar mass of the solute?

For each of the following solutions,describe the deviation with respect to Raoult's Law. -acetone (C₃H₆O) and water

For each of the following solutions,describe the deviation with respect to Raoult's Law. -hexane (C₆H₁₄) and chloroform (CHCl₃)

At 40°C,heptane has a vapor pressure of about 92.2 torr and octane has a vapor pressure of about 31.2 torr.Assuming ideal behavior,what is the vapor pressure of a solution that contains twice as many moles of heptane as octane?

A liquid-liquid solution is called an ideal solution if: I.It obeys PV = nRT. II.It obeys Raoult's law. III.Solute-solute,solvent-solvent,and solute-solvent interactions are very similar. IV.Solute-solute,solvent-solvent,and solute-solvent interactions are quite different.

A salt solution sits in an open beaker.Assuming constant temperature and pressure,the vapor pressure of the solution

A solution of CH₃OH in H₂O would most likely

A solution is made by adding 0.100 mole of ethyl ether to 0.491 mole of ethyl alcohol.If the vapor pressure of ethyl ether and ethyl alcohol at 20°C are 375 torr and 20.0 torr,respectively,the vapor pressure of the solution at 20°C (assuming ideal behavior) is:

Two liquids form a solution and release a quantity of heat.How does the pressure above the solution compare to that predicted by Raoult's law?

An ideal solution is formed from a mixture of the nonvolatile solute urea,CO(NH₂) ₂,and methanol,CH₃OH.The vapor pressure of pure methanol at 20°C is 89 mmHg.If 4.4 g of urea is mixed with 39.9 g of methanol,calculate the vapor pressure of the methanol solution.