Question 1

How much heat (in kJ) is required to convert 52.0 g of ice at $$-10.0\ ^\circ\mathrm{C} to $$steam at $$100\ ^\circ\mathrm{C}$$? Use the following data: 
Specific heat of ice: $$2.09\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Specific heat of water: $$4.18\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Specific heat of steam: $$1.84\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Molar heat of fusion: $$6.02\ \mathrm{kJ}/\mathrm{mol}$$, Molar heat of vaporization: $$40.79\ \mathrm{kJ}/\mathrm{mol}$$, Molar mass of water: $$18.02\ \mathrm{g}/\mathrm{mol}.$$

Accepted Answer

$$156\ \mathrm{kJ}$$

Question 2

A sample of $$100.\ \mathrm{g} of $$water at $$25.0\ ^\circ\mathrm{C}$$ absorbs $$50.0\ \mathrm{kJ} of $$heat. What is the final state and temperature of the sample? (Specific heat of water: $$4.184\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Molar heat of vaporization: $$40.79\ \mathrm{kJ}/\mathrm{mol}$$, Specific heat of steam: $$1.99\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Molar mass: $$18.02\ \mathrm{g}/\mathrm{mol})$$

Accepted Answer

Mixture of liquid water and steam at $$100\ ^\circ\mathrm{C}$$

Question 3

How much heat (in kJ) is released when $$1.00\ \mathrm{g} of $$steam at $$110.5\ ^\circ\mathrm{C} is $$cooled and frozen to ice at $$-22.3\ ^\circ\mathrm{C}$$? (Specific heat of ice: $$2.09\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Specific heat of water: $$4.18\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Specific heat of steam: $$1.84\ \mathrm{J}/(\mathrm{g}\cdot ^\circ\mathrm{C})$$, Molar heat of freezing: $$-6.02\ \mathrm{kJ}/\mathrm{mol}$$, Molar heat of condensation: $$-40.79\ \mathrm{kJ}/\mathrm{mol}$$, Molar mass: $$18.02\ \mathrm{g}/\mathrm{mol})$$

Accepted Answer

$$-3.41\ \mathrm{kJ}$$

Question 4

Refer to the first phase diagram (with points A, B, and C). If you start at point A and increase the temperature at constant pressure, what phase change will occur?

Accepted Answer

Sublimation

Question 5

In the first phase diagram, what phase change occurs if you start at point B and decrease the pressure at constant temperature?

Accepted Answer

Vaporization

Question 6

In the first phase diagram, what phase change occurs if you start at point C and decrease the temperature at constant pressure?

Accepted Answer

Freezing

Question 7

On a phase diagram, what is the significance of the triple point?

Accepted Answer

It is the point where solid, liquid, and gas phases coexist in equilibrium.

Question 8

On the phase diagram for compound X, what is the critical temperature?

Accepted Answer

$$600\ ^\circ\mathrm{C}$$

Question 9

If you have a bottle containing compound X at room temperature ($$25\ ^\circ\mathrm{C}) $$and $$15\ \mathrm{atm}$$ pressure, what phase is most likely present? (Refer to the phase diagram for compound X.)

Accepted Answer

Gas

Question 10

At what temperature and pressure do all three phases of compound X coexist? (Refer to the phase diagram for compound X.)

Accepted Answer

$$150\ ^\circ\mathrm{C}$$, 30\ \mathrm{atm}$

Question 11

If a bottle of compound X is at $$45\ \mathrm{atm}$$ and $$100\ ^\circ\mathrm{C}$$, what will happen if the temperature is raised to $$400\ ^\circ\mathrm{C} at $$constant pressure? (Refer to the phase diagram for compound X.)

Accepted Answer

The substance will change from liquid to gas.

Question 12

Why can’t compound X be boiled at $$200\ ^\circ\mathrm{C}$$? (Refer to the phase diagram for compound X.)

Accepted Answer

Because the vapor pressure of the liquid is too low at this temperature.

Question 13

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

Accepted Answer

The temperature and pressure above which the liquid and gas phases are indistinguishable.

Question 14

A patient receives a burn from steam at $$100\ ^\circ\mathrm{C}$$ rather than from boiling water at $$100\ ^\circ\mathrm{C}. $$Why is the burn from steam more severe?

Accepted Answer

Steam contains more energy due to the heat of vaporization.

Question 15

Which process requires the greatest input of energy for water: heating $$1.0\ \mathrm{g}$$ from $$0\ ^\circ\mathrm{C} to$$ $$100\ ^\circ\mathrm{C}$$, melting $$1.0\ \mathrm{g} of $$ice at $$0\ ^\circ\mathrm{C}$$, or vaporizing $$1.0\ \mathrm{g} of $$water at $$100\ ^\circ\mathrm{C}$$?

Accepted Answer

Vaporizing water at $$100\ ^\circ\mathrm{C}$$

Question 16

Which of the following best explains why sweating cools the human body?

Accepted Answer

Evaporation of sweat absorbs heat from the skin due to the high heat of vaporization of water.

Heating Curves and Phase Diagrams: Step-by-Step Guidance

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