Question 1

A 0.90 g sample of liquid water was introduced into an evacuated 2.00 L flask, which was then sealed and heated to 37°C. What percentage, by mass, of the water remained as liquid? [Vapor pressure of water at 37°C = 48.2 torr.]

Accepted Answer

The answer of A 0.90 g sample of liquid water...

Question 2

Flask A has a volume of 0.50 L and contains 50 g of a volatile liquid. Flask B has a volume of 1.0 L and contains 25 g of the same liquid. Both flasks are stoppered and both are at 30°C. The ratio of the vapor pressure of the liquid in Flask A to that in Flask B is:

Accepted Answer

The vapor pressure of a liquid in a closed container at a given temperature is independent of the amount of liquid. Therefore, both flasks will have the same vapor pressure since they contain the same liquid at the same temperature, leading to a ratio of 1:1.

Question 3

Arrange the following compounds in order of increasing boiling point: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH)CH₂OH; III) 1,2,3-propanetriol, (glycerol), HOCH₂CH(OH)CH₂OH.

Accepted Answer

The boiling point increases with the number of hydroxyl groups due to increased hydrogen bonding. 1-propanol has one OH group, 1,2-propanediol has two, and glycerol has three, leading to the order: I, II, III.

Question 4

The heat of deposition equals the negative of the heat of ________.

Accepted Answer

The answer of The heat of deposition equals the negative...

Question 5

Given the data below, determine the molar enthalpy change of vaporization of liquid Rb. Rb, P1 = 1.00 mmHg, t1 = 297°C, P2 = 400 mmHg, t2 = 620°C

Accepted Answer

The molar enthalpy change of vaporization can be calculated using the Clausius-Clapeyron equation. By converting temperatures to Kelvin and using the given pressures, the calculation yields approximately 78.5 kJ/mol.

Question 6

The normal boiling point of acetone is 56.2°C and the molar heat of vaporization is 32.0 kJ/mol. At what temperature will acetone boil under a pressure of 50.0 mmHg?

Accepted Answer

The answer of The normal boiling point of acetone is...

Question 7

How much heat would be released by the condensation of 5.40 g of steam at 100°C and the subsequent cooling of the water to 25°C? [ΔHvap = 40.7 kJ/mol at 100°C; Cp for H₂O(l) is 4.18 J g-1 °C-1]

Accepted Answer

First, calculate the moles of steam: 5.40 g / 18.015 g/mol = 0.2998 mol. The heat released during condensation is 0.2998 mol * 40.7 kJ/mol = 12.2 kJ. Then, calculate the heat released when cooling the water: 5.40 g * 4.18 J/g°C * (100°C - 25°C) = 1.69 kJ. Total heat released = 12.2 kJ + 1.69 kJ = 13.9 kJ.

Question 8

A liquid has a molar heat of vaporization of 22.7 kJ/mol. Its normal boiling point is 459K. What is the vapor pressure, in mmHg, at 70°C?

Accepted Answer

The Clausius-Clapeyron equation can be used to calculate the vapor pressure at a new temperature given the heat of vaporization and the normal boiling point. The equation is ln(P1/P2) = ΔHvap/R * (1/T2 - 1/T1), where ΔHvap is the molar heat of vaporization, R is the gas constant (8.314 J/mol·K), T1 is the normal boiling point in Kelvin, and T2 is the new temperature in Kelvin. Converting 70°C to Kelvin gives 343K. Since the normal boiling point is 459K, where the vapor pressure equals 760 mmHg (standard atmospheric pressure), we can solve for P2, the vapor pressure at 343K. The calculation shows that the vapor pressure at 70°C is closest to 102 mmHg, making option A correct.

Question 9

The factor that has the largest effect on vapor pressure is ________.

Accepted Answer

The presence of hydrogen bonding has the largest effect on vapor pressure due to the strong intermolecular forces that must be overcome for a molecule to escape into the gas phase. As a result, liquids with stronger hydrogen bonding (like water) have lower vapor pressures than liquids with weaker or no hydrogen bonding (like ethanol or pentane).

Question 10

What would be the appropriate equilibrium temperature of a system obtained by adding 25.0 g of ice at 0°C to 250.0 mL of "hot" (80°C) coffee, assuming that the heat capacity and density of the coffee are the same as for pure water (4.18 J g-1 °C-1 and 0.997 g mL-1), and also assuming negligible heat transfer with the surroundings? [For water, ΔHfusion = 6.02 kJ/mol.]

Accepted Answer

First, we need to calculate the amount of heat required to melt the ice:
q_ice = (25.0 g) x (6.02 kJ/mol) / (18.02 g/mol) = 8.344 kJ

Next, we need to calculate the amount of heat lost by the coffee as it cools down:
q_coffee = (250.0 mL) x (0.997 g/mL) x (4.18 J/g°C) x (80°C - T)

Since the heat lost by the coffee is equal to the heat gained by the ice, we can set the two equations equal to each other and solve for T:
8.344 kJ = (250.0 mL) x (0.997 g/mL) x (4.18 J/g°C) x (80°C - T)

Simplifying the equation, we get:
T = 65°C

Question 11

Liquid and vapor phases of a substance become indistinguishable at the ________.

Accepted Answer

The critical point is the temperature and pressure at which the liquid and vapor phases of a substance become indistinguishable. This is where the distinction between the two phases disappears and the substance behaves as a supercritical fluid. A, B, C, and E are not relevant points for this phenomenon.

Question 12

The maximum temperature at which a gas can be liquefied is just below the ________.

Accepted Answer

The critical temperature is the temperature above which a gas cannot be liquefied, regardless of the pressure applied. Therefore, the maximum temperature at which a gas can be liquefied is just below the critical temperature.

Question 13

Given the data below, determine the normal boiling point of COCl₂. P1 = 100 mmHg, t1 = -35.6°C, ΔHvap = 27.4 kJ/mol

Accepted Answer

The normal boiling point is the temperature at which the vapor pressure equals 760 mmHg. Using the Clausius-Clapeyron equation, we can estimate the boiling point at 760 mmHg given the vapor pressure at 100 mmHg and the enthalpy of vaporization. Solving this gives approximately 5.0°C.

Question 14

Arrange the following compounds in order of increasing viscosity: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH)CH₂OH; III) 1,2,3-propanetriol, (glycerol), HOCH₂CH(OH)CH₂OH.

Accepted Answer

Viscosity increases with the number of hydroxyl (OH) groups due to increased hydrogen bonding. Therefore, 1-propanol (I) has the lowest viscosity, followed by 1,2-propanediol (II), and 1,2,3-propanetriol (III) has the highest viscosity.

Question 15

Given the data below, determine the normal boiling point of liquid Rb. P1 = 400 mmHg, t1 = 620°C, ΔHvap = 78.5 kJ/mol

Accepted Answer

The answer of Given the data below, determine the normal...

Question 16

The relationship between the vapor pressure of a liquid and temperature can be expressed by the Clausius-Clapeyron equation: Log[P2/P1] = [ΔHvap/R] × [1/T1 - 1/T2] Ethanol (C₂H₅OH) has a normal boiling point of 78.3°C and, with ΔHvap = 39.3 kJ/mol. What is the vapor pressure of ethanol at 50.0°C?

Accepted Answer

First, we need to convert the given temperatures into Kelvin:

T1 = 78.3°C + 273.15 = 351.45 K (normal boiling point)
T2 = 50.0°C + 273.15 = 323.15 K

Next, we can use the Clausius-Clapeyron equation:

Log[P2/P1] = [ΔHvap/R] × [1/T1 - 1/T2]

We know ΔHvap = 39.3 kJ/mol, and R = 8.314 J/(mol*K). Converting ΔHvap to J/mol:

ΔHvap = 39.3 kJ/mol × 1000 J/kJ = 39300 J/mol

Substituting the values:

Log[P2/1 atm] = (39300 J/mol / (8.314 J/(mol*K))) × (1/351.45 K - 1/323.15 K)

Solving for Log[P2/1 atm]:

Log[P2/1 atm] = -6.356

Taking antilog of both sides:

P2/1 atm = 2.34 × 10^-7

Multiplying both sides by 760 torr (because 1 atm = 760 torr):

P2 = 2.34 × 10^-7 atm × 760 torr/atm = 0.178 torr

Rounding to 3 significant figures, the vapor pressure of ethanol at 50.0°C is 0.178 torr, which is closest to answer choice B (234 torr).

Question 17

A substance has a heat of fusion of 61.5 kJ/mol and a heat of deposition of -167.4 kJ/mol. What is the heat of sublimation in kJ/mol?

Accepted Answer

The answer of A substance has a heat of fusion...

Question 18

When the vapor pressure of a liquid equals atmospheric pressure, the temperature of the liquid equals ________.

Accepted Answer

When the vapor pressure of a liquid equals atmospheric pressure, it means that the liquid has reached its boiling point, which is when it can turn into a gas. Therefore, the temperature of the liquid equals the boiling point. Choice B is the correct answer because it specifically mentions the boiling point.

Question 19

The temperature at which the vapor pressure of a liquid equals the external pressure is called the ________.

Accepted Answer

The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure. At this point, the liquid changes into its vapor state. Therefore, option A is the correct answer.

Option B, critical point, is the temperature and pressure at which the gas and liquid states of a substance become identical, and properties such as density, heat capacity, and thermal expansion are infinite.

Option C, melting point, is the temperature at which a solid melts and turns into a liquid.

Option D, sublimation point, is the temperature at which a solid converts into gas without going through the liquid phase.

Option E, thermal point, is not a scientific term used commonly in chemistry or physics.

Question 20

Given the data below, determine the molar enthalpy change of vaporization of COCl₂. COCl₂, P1 = 40 mmHg, t1 = -50.3°C, P2 = 100 mmHg, t2 = -35.6°C

Accepted Answer

The molar enthalpy change of vaporization can be calculated using the Clausius-Clapeyron equation. Given the pressures and temperatures, the calculation yields approximately 27.4 kJ/mol.

Quiz 12: Intermolecular Forces: Liquids and Solids

A 0.90 g sample of liquid water was introduced into an evacuated 2.00 L flask, which was then sealed and heated to 37°C. What percentage, by mass, of the water remained as liquid? [Vapor pressure of water at 37°C = 48.2 torr.]

Flask A has a volume of 0.50 L and contains 50 g of a volatile liquid. Flask B has a volume of 1.0 L and contains 25 g of the same liquid. Both flasks are stoppered and both are at 30°C. The ratio of the vapor pressure of the liquid in Flask A to that in Flask B is:

Arrange the following compounds in order of increasing boiling point: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH) CH₂OH; III) 1,2,3-propanetriol, (glycerol) , HOCH₂CH(OH) CH₂OH.

The heat of deposition equals the negative of the heat of ________.

Given the data below, determine the molar enthalpy change of vaporization of liquid Rb. Rb, P1 = 1.00 mmHg, t1 = 297°C, P2 = 400 mmHg, t2 = 620°C

The normal boiling point of acetone is 56.2°C and the molar heat of vaporization is 32.0 kJ/mol. At what temperature will acetone boil under a pressure of 50.0 mmHg?

How much heat would be released by the condensation of 5.40 g of steam at 100°C and the subsequent cooling of the water to 25°C? [ΔHvap = 40.7 kJ/mol at 100°C; Cp for H₂O(l) is 4.18 J g-1 °C-1]

A liquid has a molar heat of vaporization of 22.7 kJ/mol. Its normal boiling point is 459K. What is the vapor pressure, in mmHg, at 70°C?

The factor that has the largest effect on vapor pressure is ________.

Liquid and vapor phases of a substance become indistinguishable at the ________.

The maximum temperature at which a gas can be liquefied is just below the ________.

Given the data below, determine the normal boiling point of COCl₂. P1 = 100 mmHg, t1 = -35.6°C, ΔHvap = 27.4 kJ/mol

Arrange the following compounds in order of increasing viscosity: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH) CH₂OH; III) 1,2,3-propanetriol, (glycerol) , HOCH₂CH(OH) CH₂OH.

Given the data below, determine the normal boiling point of liquid Rb. P1 = 400 mmHg, t1 = 620°C, ΔHvap = 78.5 kJ/mol

A substance has a heat of fusion of 61.5 kJ/mol and a heat of deposition of -167.4 kJ/mol. What is the heat of sublimation in kJ/mol?

When the vapor pressure of a liquid equals atmospheric pressure, the temperature of the liquid equals ________.

The temperature at which the vapor pressure of a liquid equals the external pressure is called the ________.

Given the data below, determine the molar enthalpy change of vaporization of COCl₂. COCl₂, P1 = 40 mmHg, t1 = -50.3°C, P2 = 100 mmHg, t2 = -35.6°C

Quiz 12: Intermolecular Forces: Liquids and Solids

A 0.90 g sample of liquid water was introduced into an evacuated 2.00 L flask, which was then sealed and heated to 37°C. What percentage, by mass, of the water remained as liquid? [Vapor pressure of water at 37°C = 48.2 torr.]

Flask A has a volume of 0.50 L and contains 50 g of a volatile liquid. Flask B has a volume of 1.0 L and contains 25 g of the same liquid. Both flasks are stoppered and both are at 30°C. The ratio of the vapor pressure of the liquid in Flask A to that in Flask B is:

Arrange the following compounds in order of increasing boiling point: I) 1-propanol, CH3CH2CH2OH; II) 1,2-propanediol, CH3CH(OH) CH2OH; III) 1,2,3-propanetriol, (glycerol) , HOCH2CH(OH) CH2OH.

The heat of deposition equals the negative of the heat of ________.

Given the data below, determine the molar enthalpy change of vaporization of liquid Rb. Rb, P1 = 1.00 mmHg, t1 = 297°C, P2 = 400 mmHg, t2 = 620°C

The normal boiling point of acetone is 56.2°C and the molar heat of vaporization is 32.0 kJ/mol. At what temperature will acetone boil under a pressure of 50.0 mmHg?

How much heat would be released by the condensation of 5.40 g of steam at 100°C and the subsequent cooling of the water to 25°C? [ΔHvap = 40.7 kJ/mol at 100°C; Cp for H2O(l) is 4.18 J g-1 °C-1]

A liquid has a molar heat of vaporization of 22.7 kJ/mol. Its normal boiling point is 459K. What is the vapor pressure, in mmHg, at 70°C?

The factor that has the largest effect on vapor pressure is ________.

Liquid and vapor phases of a substance become indistinguishable at the ________.

The maximum temperature at which a gas can be liquefied is just below the ________.

Given the data below, determine the normal boiling point of COCl2. P1 = 100 mmHg, t1 = -35.6°C, ΔHvap = 27.4 kJ/mol

Arrange the following compounds in order of increasing viscosity: I) 1-propanol, CH3CH2CH2OH; II) 1,2-propanediol, CH3CH(OH) CH2OH; III) 1,2,3-propanetriol, (glycerol) , HOCH2CH(OH) CH2OH.

Given the data below, determine the normal boiling point of liquid Rb. P1 = 400 mmHg, t1 = 620°C, ΔHvap = 78.5 kJ/mol

A substance has a heat of fusion of 61.5 kJ/mol and a heat of deposition of -167.4 kJ/mol. What is the heat of sublimation in kJ/mol?

When the vapor pressure of a liquid equals atmospheric pressure, the temperature of the liquid equals ________.

The temperature at which the vapor pressure of a liquid equals the external pressure is called the ________.

Given the data below, determine the molar enthalpy change of vaporization of COCl2. COCl2, P1 = 40 mmHg, t1 = -50.3°C, P2 = 100 mmHg, t2 = -35.6°C

Arrange the following compounds in order of increasing boiling point: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH) CH₂OH; III) 1,2,3-propanetriol, (glycerol) , HOCH₂CH(OH) CH₂OH.

How much heat would be released by the condensation of 5.40 g of steam at 100°C and the subsequent cooling of the water to 25°C? [ΔHvap = 40.7 kJ/mol at 100°C; Cp for H₂O(l) is 4.18 J g-1 °C-1]

Given the data below, determine the normal boiling point of COCl₂. P1 = 100 mmHg, t1 = -35.6°C, ΔHvap = 27.4 kJ/mol

Arrange the following compounds in order of increasing viscosity: I) 1-propanol, CH₃CH₂CH₂OH; II) 1,2-propanediol, CH₃CH(OH) CH₂OH; III) 1,2,3-propanetriol, (glycerol) , HOCH₂CH(OH) CH₂OH.

Given the data below, determine the molar enthalpy change of vaporization of COCl₂. COCl₂, P1 = 40 mmHg, t1 = -50.3°C, P2 = 100 mmHg, t2 = -35.6°C