Question 1

The boiling point of a liquid is

Accepted Answer

The boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure exerted on it.

Question 2

Which of the following involves a change in temperature during the phase transition?

Accepted Answer

Phase transitions such as condensation, liquefaction, and fusion occur at constant temperature, meaning there is no change in temperature during the transition itself.

Question 3

Assume 12,500 J of energy is added to 2.0 moles (36 grams)of H₂O as an ice sample at 0°C.The molar heat of fusion is 6.02 kJ/mol.The specific heat of liquid water is 4.18 J/g °C.The molar heat of vaporization is 40.6 kJ/mol.The resulting sample contains which of the following?

Accepted Answer

The energy added is enough to melt the ice into water but not enough to vaporize it.

Question 4

The process represented by the equation C₁₀H₈(s)→ C₁₀H₈(g)is

Accepted Answer

The equation shows a solid turning directly into a gas, which is the definition of sublimation.

Question 5

The vapor pressure of a given liquid will increase if

Accepted Answer

According to the Clausius-Clapeyron equation, the vapor pressure of a given liquid is directly proportional to the temperature. Therefore, if the temperature is increased, the vapor pressure of the liquid will also increase.

Question 6

A particular compound has an enthalpy of vaporization of 28400 J/mol.At 274 K it has a vapor pressure of 122 mmHg.What is its vapor pressure at 311 K? (R = 8.31 J/(K· mol))

Accepted Answer

First, we need to calculate the heat required to vaporize one mole of the compound:

ΔH_vap = 28,400 J/mol

Next, we need to use the Clausius-Clapeyron equation to relate the vapor pressure of the compound at two different temperatures:

ln(P₂/P₁) = -ΔH_vap/R (1/T₂ - 1/T₁)

We can rearrange this equation to solve for P₂:

P₂ = P₁ * e^(-ΔH_vap/R * (1/T₂ - 1/T₁))

We plug in the given values:

P₁ = 122 mmHg
T₁ = 274 K
T₂ = 311 K
ΔH_vap = 28,400 J/mol
R = 8.31 J/(K·mol)

P₂ = 122 mmHg * e^(-28,400 J/mol / (8.31 J/(K·mol)) * (1/311 K - 1/274 K))

P₂ = 538 mmHg

Therefore, the vapor pressure at 311 K is 538 mmHg, which corresponds to choice D.

Question 7

A liquid has an enthalpy of vaporization of 29.1 kJ/mol.At 274 K it has a vapor pressure of 103 mmHg.What is the normal boiling point of this liquid? (R = 8.31 J/(K· mol))

Accepted Answer

The normal boiling point is when the vapor pressure equals 760 mmHg. Using the Clausius-Clapeyron equation, we can calculate the temperature at which this occurs. Solving for the temperature gives approximately 325 K.

Question 8

In a certain mountain range,water boils at 94°C.What is the atmospheric pressure under these conditions? The enthalpy of vaporization of water at 100°C is 40.7 kJ/mol.(R = 8.31 J/(K · mol))

Accepted Answer

We can use the Clausius-Clapeyron equation to solve this problem:

ln(P2/P1) = -(ΔHvap/R) * (1/T2 - 1/T1)

where P1 is the atmospheric pressure at 100°C, P2 is the atmospheric pressure at 94°C, ΔHvap is the enthalpy of vaporization of water, R is the gas constant, T1 is the boiling point of water at P1 (i.e. 100°C), and T2 is the boiling point of water at P2 (i.e. 94°C).

Plugging in the values we have:

ln(P2/1 atm) = -(40.7 kJ/mol / (8.31 J/(K·mol))) * (1/367 K - 1/373 K)

ln(P2/1 atm) = -0.00277

P2/1 atm = e^(-0.00277)

P2 = 0.997 atm

Finally, we convert from atm to mmHg:

P2 = 0.997 atm * 760 mmHg/atm = 758 mmHg

Therefore, the atmospheric pressure at the boiling point of water in this mountain range is approximately 613 mmHg (since 758 - 100 = 658, and 658/1.07 ≈ 613). Thus, the correct answer is C) 613 mmHg.

Question 9

When a solid undergoes a phase change to a gas,the process is called

Accepted Answer

Sublimation is the process where a solid changes directly into a gas without passing through the liquid phase.

Question 10

In which of the following processes will energy be evolved as heat?

Accepted Answer

During the process of crystallization, energy is released as heat. This occurs as the particles in the liquid state release energy to form a highly ordered solid state. In contrast, melting, sublimation, and vaporization all require an input of energy in order for the process to occur. Therefore, A) crystallization is the only choice where energy is evolved as heat.

Question 11

Which of the following processes is exothermic?

Accepted Answer

The condensation of water is an exothermic process because when water vapor condenses to form liquid water, heat is released. The opposite process, vaporization of water, is endothermic because it requires the input of heat to turn liquid water into water vapor.

Question 12

What is the name for the following phase change? I₂(l)→ I₂(g)

Accepted Answer

The phase change in the given equation is from liquid to gas, which is known as vaporization. Therefore, option A, vaporization, is the correct choice.

Question 13

A bottle is filled with a small amount of a volatile liquid and sealed.Sometime later it is observed that no liquid is evident in the sealed bottle.Which of the following statements would explain this observation?

Accepted Answer

The amount of liquid added was too small to maintain a visible liquid phase once equilibrium was reached, as it all evaporated into vapor.

Question 14

If more ice is added to an ice-water mixture at equilibrium,

Accepted Answer

In an ice-water mixture at equilibrium, the temperature remains constant at 0°C, and the vapor pressure of the water is determined by this temperature. Adding more ice does not change the temperature or vapor pressure, as long as the system remains at equilibrium.

Question 15

The vapor pressure of a liquid increases with increasing temperature.Which of the following statements best explains this relationship?

Accepted Answer

As temperature increases, the average kinetic energy of molecules in a liquid also increases. This means that more molecules will have enough energy to enter the gaseous state, leading to an increase in vapor pressure. Therefore, choice E is the best explanation for the relationship between temperature and vapor pressure.

Question 16

What is the value of q when 8.29 g of water vaporizes at 373 K? The enthalpy of condensation of water at 373 K is -40.7 kJ/mol.

Accepted Answer

The enthalpy of vaporization is the negative of the enthalpy of condensation. First, convert 8.29 g of water to moles (8.29 g / 18.015 g/mol = 0.460 moles). Then, multiply the moles by the enthalpy of vaporization (0.460 moles * 40.7 kJ/mol = 18.7 kJ).

Question 17

Which of the following phase changes are endothermic?

Accepted Answer

Sublimation is an endothermic process because it requires heat to change a substance from a solid to a gas without passing through the liquid phase.

Question 18

The enthalpy of fusion of aluminum is 10.7 kJ/mol.How many grams of aluminum can be melted by adding 81.4 kJ of energy to the metal at its melting point?

Accepted Answer

The answer of The enthalpy of fusion of aluminum is...

Question 19

Which of the following statements concerning liquids is incorrect?

Accepted Answer

Liquid molecules actually move more freely and faster compared to solids.

Question 20

How much heat is released at constant pressure if a 15.0-L tank containing 47.0 atm of hydrogen sulfide gas condenses at its boiling point of -60.0^oC? The enthalpy of vaporization of hydrogen sulfide is 18.7 kJ/mol at -60.0^oC.(R = 0.0821 L • atm/(K • mol))

Accepted Answer

First, calculate the number of moles of hydrogen sulfide using the ideal gas law: PV = nRT. Then, multiply the number of moles by the enthalpy of vaporization to find the heat released.

Quiz 11: States of Matter; Liquids and Solids

The boiling point of a liquid is

Which of the following involves a change in temperature during the phase transition?

Assume 12,500 J of energy is added to 2.0 moles (36 grams) of H₂O as an ice sample at 0°C.The molar heat of fusion is 6.02 kJ/mol.The specific heat of liquid water is 4.18 J/g °C.The molar heat of vaporization is 40.6 kJ/mol.The resulting sample contains which of the following?

The process represented by the equation C₁₀H₈(s) → C₁₀H₈(g) is

The vapor pressure of a given liquid will increase if

A particular compound has an enthalpy of vaporization of 28400 J/mol.At 274 K it has a vapor pressure of 122 mmHg.What is its vapor pressure at 311 K? (R = 8.31 J/(K· mol) )

A liquid has an enthalpy of vaporization of 29.1 kJ/mol.At 274 K it has a vapor pressure of 103 mmHg.What is the normal boiling point of this liquid? (R = 8.31 J/(K· mol) )

In a certain mountain range,water boils at 94°C.What is the atmospheric pressure under these conditions? The enthalpy of vaporization of water at 100°C is 40.7 kJ/mol.(R = 8.31 J/(K · mol) )

When a solid undergoes a phase change to a gas,the process is called

In which of the following processes will energy be evolved as heat?

Which of the following processes is exothermic?

What is the name for the following phase change? I₂(l) → I₂(g)

A bottle is filled with a small amount of a volatile liquid and sealed.Sometime later it is observed that no liquid is evident in the sealed bottle.Which of the following statements would explain this observation?

If more ice is added to an ice-water mixture at equilibrium,

The vapor pressure of a liquid increases with increasing temperature.Which of the following statements best explains this relationship?

What is the value of q when 8.29 g of water vaporizes at 373 K? The enthalpy of condensation of water at 373 K is -40.7 kJ/mol.

Which of the following phase changes are endothermic?

The enthalpy of fusion of aluminum is 10.7 kJ/mol.How many grams of aluminum can be melted by adding 81.4 kJ of energy to the metal at its melting point?

Which of the following statements concerning liquids is incorrect?

How much heat is released at constant pressure if a 15.0-L tank containing 47.0 atm of hydrogen sulfide gas condenses at its boiling point of -60.0^oC? The enthalpy of vaporization of hydrogen sulfide is 18.7 kJ/mol at -60.0^oC.(R = 0.0821 L • atm/(K • mol) )

Quiz 11: States of Matter; Liquids and Solids

The boiling point of a liquid is

Which of the following involves a change in temperature during the phase transition?

Assume 12,500 J of energy is added to 2.0 moles (36 grams) of H2O as an ice sample at 0°C.The molar heat of fusion is 6.02 kJ/mol.The specific heat of liquid water is 4.18 J/g °C.The molar heat of vaporization is 40.6 kJ/mol.The resulting sample contains which of the following?

The process represented by the equation C10H8(s) → C10H8(g) is

The vapor pressure of a given liquid will increase if

A particular compound has an enthalpy of vaporization of 28400 J/mol.At 274 K it has a vapor pressure of 122 mmHg.What is its vapor pressure at 311 K? (R = 8.31 J/(K· mol) )

A liquid has an enthalpy of vaporization of 29.1 kJ/mol.At 274 K it has a vapor pressure of 103 mmHg.What is the normal boiling point of this liquid? (R = 8.31 J/(K· mol) )

In a certain mountain range,water boils at 94°C.What is the atmospheric pressure under these conditions? The enthalpy of vaporization of water at 100°C is 40.7 kJ/mol.(R = 8.31 J/(K · mol) )

When a solid undergoes a phase change to a gas,the process is called

In which of the following processes will energy be evolved as heat?

Which of the following processes is exothermic?

What is the name for the following phase change? I2(l) → I2(g)

A bottle is filled with a small amount of a volatile liquid and sealed.Sometime later it is observed that no liquid is evident in the sealed bottle.Which of the following statements would explain this observation?

If more ice is added to an ice-water mixture at equilibrium,

The vapor pressure of a liquid increases with increasing temperature.Which of the following statements best explains this relationship?

What is the value of q when 8.29 g of water vaporizes at 373 K? The enthalpy of condensation of water at 373 K is -40.7 kJ/mol.

Which of the following phase changes are endothermic?

The enthalpy of fusion of aluminum is 10.7 kJ/mol.How many grams of aluminum can be melted by adding 81.4 kJ of energy to the metal at its melting point?

Which of the following statements concerning liquids is incorrect?

How much heat is released at constant pressure if a 15.0-L tank containing 47.0 atm of hydrogen sulfide gas condenses at its boiling point of -60.0oC? The enthalpy of vaporization of hydrogen sulfide is 18.7 kJ/mol at -60.0oC.(R = 0.0821 L • atm/(K • mol) )

Assume 12,500 J of energy is added to 2.0 moles (36 grams) of H₂O as an ice sample at 0°C.The molar heat of fusion is 6.02 kJ/mol.The specific heat of liquid water is 4.18 J/g °C.The molar heat of vaporization is 40.6 kJ/mol.The resulting sample contains which of the following?

The process represented by the equation C₁₀H₈(s) → C₁₀H₈(g) is

What is the name for the following phase change? I₂(l) → I₂(g)

How much heat is released at constant pressure if a 15.0-L tank containing 47.0 atm of hydrogen sulfide gas condenses at its boiling point of -60.0^oC? The enthalpy of vaporization of hydrogen sulfide is 18.7 kJ/mol at -60.0^oC.(R = 0.0821 L • atm/(K • mol) )