Q: What is the correct formula to calculate the heat required to raise the temperature of a substance without a phase change?

$q = m \times C_s \times \Delta T$

Question 1

Which of the following best describes the process of sublimation?

Accepted Answer

Transition from solid to gas

Question 2

During the boiling of water, what happens to the average kinetic energy of the molecules remaining in the liquid?

Accepted Answer

It decreases because the highest-energy molecules leave

Question 3

Which enthalpy is typically larger for a given substance: $\Delta H_{fus}$ or $\Delta H_{vap}$?

Accepted Answer

$\Delta H_{vap}$

Question 4

How can the enthalpy of sublimation ($\Delta H_{sub}$) be calculated for a substance?

Accepted Answer

$\Delta H_{sub} = \Delta H_{fus} + \Delta H_{vap}$

Question 5

What is the correct formula to calculate the heat required to raise the temperature of a substance without a phase change?

Accepted Answer

$q = m 	imes C_s 	imes \Delta T$

Question 6

A sample of 1.00 mol H$_2$O(s) is heated from $-25.0^\circ$C to $0.0^\circ$C. If the specific heat of ice is $2.09 \ \mathrm{J} \ g^{-1} \ ^\circ C^{-1}$, what is the heat required? (Molar mass of H$_2$O = 18.0 g/mol)

Accepted Answer

$q = 0.941 \ \mathrm{kJ}$

Question 7

Which segment of a heating curve represents a phase change?

Accepted Answer

A segment with a horizontal line

Question 8

What is the value of $q$ for boiling 1.00 mol of H$_2$O at 100.0$^\circ$C if $\Delta H_{vap} = 40.7 \ \mathrm{kJ} \ mol^{-1}$?

Accepted Answer

$40.7 \ \mathrm{kJ}$

Question 9

Which of the following best describes the triple point on a phase diagram?

Accepted Answer

The temperature and pressure where solid, liquid, and gas phases coexist

Question 10

If you increase the pressure at a constant temperature on a phase diagram for water, which phase transition are you most likely to observe?

Accepted Answer

Gas to liquid

Question 11

What is the value of $q$ for heating 1.00 mol of H$_2$O(g) from 100.0$^\circ$C to 125.0$^\circ$C if $C_{s,gas} = 2.01 \ \mathrm{J} \ g^{-1} \ ^\circ C^{-1}$?

Accepted Answer

$0.904 \ \mathrm{kJ}$

Question 12

Which of the following statements about the critical point on a phase diagram is correct?

Accepted Answer

It is the highest temperature and pressure at which a liquid can exist

Question 13

Which equation would you use to calculate the heat required to melt 1.00 mol of ice at 0.0$^\circ$C?

Accepted Answer

$q = n 	imes \Delta H_{fus}$

Question 14

Which of the following best explains why $\Delta H_{vap}$ is typically larger than $\Delta H_{fus}$?

Accepted Answer

Vaporization requires breaking all intermolecular forces, while fusion only partially disrupts them

Question 15

A sample of water is at its triple point. Which phases are present?

Accepted Answer

Solid, liquid, and gas

Question 16

Which segment of the heating curve for H$_2$O represents the heating of liquid water from 0.0$^\circ$C to 100.0$^\circ$C?

Accepted Answer

Segment 3

Question 17

If you cool water vapor at constant pressure, which phase change will occur first according to the phase diagram?

Accepted Answer

Condensation (gas to liquid)

Question 18

Which of the following is the correct definition of specific heat capacity?

Accepted Answer

The amount of heat required to change the temperature of 1 g of a substance by 1$^\circ$C

Intermolecular Forces, Phase Changes, and Phase Diagrams

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