9.9: Solids, Liquids, and Gases (Exercises)

Many of the questions here were taken from the Central Science Texboom Map, or the OpenStax Texbook map. For additional practice using the ideas covered in this chapter, please see the links found at this source.

9.1: The Solid State of Matter

Q9.1.1

At very low temperatures oxygen, O₂, freezes and forms a crystalline solid. Which best describes these crystals?

1. ionic
2. covalent network
3. metallic
4. molecular crystals

Q9.1.2

Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:

1. SiO₂
2. KCl
3. Cu
4. CO₂
5. C (diamond)
6. BaSO₄
7. NH₃
8. NH₄F
9. C₂H₅OH

S9.1.2

(a) SiO₂, covalent network; (b) KCl, ionic; (c) Cu, metallic; (d) CO, molecular; (e) C (diamond), covalent network; (f) BaSO₄, ionic; (g) NH₃, molecular; (h) NH₄F, ionic; (i) C₂H₅OH, molecular

Q9.1.3

Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:

1. CaCl₂
2. SiC
3. N₂
4. Fe
5. C (graphite)
6. CH₃CH₂CH₂CH₃
7. HCl
8. NH₄NO₃
9. K₃PO₄

Q9.1.4

Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:

Substance	Appearance	Melting Point	Electrical Conductivity	Solubility in Water
X	lustrous, malleable	1500 °C	high	insoluble
Y	soft, yellow	113 °C	none	insoluble
Z	hard, white	800 °C	only if melted/dissolved	soluble

S9.1.4

X = metallic; Y = covalent network; Z = ionic

Q9.1.5

Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:

Substance	Appearance	Melting Point	Electrical Conductivity	Solubility in Water
X	brittle, white	800 °C	only if melted/dissolved	soluble
Y	shiny, malleable	1100 °C	high	insoluble
Z	hard, colorless	3550 °C	none	insoluble

Q9.1.6

Identify the following substances as ionic, metallic, covalent network, or molecular solids:

Substance A is malleable, ductile, conducts electricity well, and has a melting point of 1135 °C. Substance B is brittle, does not conduct electricity as a solid but does when molten, and has a melting point of 2072 °C. Substance C is very hard, does not conduct electricity, and has a melting point of 3440 °C. Substance D is soft, does not conduct electricity, and has a melting point of 185 °C.

Q9.1.7

Substance A is shiny, conducts electricity well, and melts at 975 °C. Substance A is likely a(n):

1. ionic solid
2. metallic solid
3. molecular solid
4. covalent network solid

S9.1.7

(b) metallic solid

Q9.1.8

Substance B is hard, does not conduct electricity, and melts at 1200 °C. Substance B is likely a(n):

1. ionic solid
2. metallic solid
3. molecular solid
4. covalent network solid

9.2: Properties of Liquids

Q9.2.1

The test tubes shown here contain equal amounts of the specified motor oils. Identical metal spheres were dropped at the same time into each of the tubes, and a brief moment later, the spheres had fallen to the heights indicated in the illustration. Rank the motor oils in order of increasing viscosity, and explain your reasoning:

Q9.2.2

Although steel is denser than water, a steel needle or paper clip placed carefully lengthwise on the surface of still water can be made to float. Explain at a molecular level how this is possible:

(credit: Cory Zanker)

S9.2.2

The water molecules have strong intermolecular forces of hydrogen bonding. The water molecules are thus attracted strongly to one another and exhibit a relatively large surface tension, forming a type of “skin” at its surface. This skin can support a bug or paper clip if gently placed on the water.

Q9.2.3

The surface tension and viscosity values for diethyl ether, acetone, ethanol, and ethylene glycol are shown here.

1. Explain their differences in viscosity in terms of the size and shape of their molecules and their IMFs.
2. Explain their differences in surface tension in terms of the size and shape of their molecules and their IMFs:

Q9.2.4

You may have heard someone use the figure of speech “slower than molasses in winter” to describe a process that occurs slowly. Explain why this is an apt idiom, using concepts of molecular size and shape, molecular interactions, and the effect of changing temperature.

S9.2.4

Temperature has an effect on intermolecular forces: the higher the temperature, the greater the kinetic energies of the molecules and the greater the extent to which their intermolecular forces are overcome, and so the more fluid (less viscous) the liquid; the lower the temperature, the lesser the intermolecular forces are overcome, and so the less viscous the liquid.

Q9.2.5

It is often recommended that you let your car engine run idle to warm up before driving, especially on cold winter days. While the benefit of prolonged idling is dubious, it is certainly true that a warm engine is more fuel efficient than a cold one. Explain the reason for this.

0.809 atm; 82.0 kPa

Q9.3.1

A typical barometric pressure in Kansas City is 740 torr. What is this pressure in atmospheres, in millimeters of mercury, and in kilopascals?

Q9.3.2

Canadian tire pressure gauges are marked in units of kilopascals. What reading on such a gauge corresponds to 32 psi?

S9.3.2

2.2 × 10² kPa

Q9.3.3

During the Viking landings on Mars, the atmospheric pressure was determined to be on the average about 6.50 millibars (1 bar = 0.987 atm). What is that pressure in torr and kPa?

Q9.3.4

The pressure of the atmosphere on the surface of the planet Venus is about 88.8 atm. Compare that pressure in psi to the normal pressure on earth at sea level in psi.

S9.3.4

Earth: 14.7 lb in^–2; Venus: 13.1× 10³ lb in⁻²

Q9.3.5

A medical laboratory catalog describes the pressure in a cylinder of a gas as 14.82 MPa. What is the pressure of this gas in atmospheres and torr?

Q9.4.1

Using the postulates of the kinetic molecular theory, explain why a gas uniformly fills a container of any shape.

Q9.4.2

Can the speed of a given molecule in a gas double at constant temperature? Explain your answer.

S9.4.2

Yes. At any given instant, there are a range of values of molecular speeds in a sample of gas. Any single molecule can speed up or slow down as it collides with other molecules. The average velocity of all the molecules is constant at constant temperature.

Q9.4.3

Describe what happens to the average kinetic energy of ideal gas molecules when the conditions are changed as follows:

1. The pressure of the gas is increased by reducing the volume at constant temperature.
2. The pressure of the gas is increased by increasing the temperature at constant volume.
3. The average velocity of the molecules is increased by a factor of 2.

Q9.5.1

A 1.00 mol sample of gas at 25°C and 1.0 atm has an initial volume of 22.4 L. Calculate the results of each change, assuming all the other conditions remain constant.

1. The pressure is changed to 85.7 mmHg. How many milliliters does the gas occupy?
2. The volume is reduced to 275 mL. What is the pressure in millimeters of mercury?
3. The pressure is increased to 25.3 atm. What is the temperature in degrees Celsius?
4. The sample is heated to 30°C. What is the volume in liters?
5. The sample is compressed to 1255 mL, and the pressure is increased to 2555 torr. What is the temperature of the gas in kelvins?

Q9.5.2

A 1.00 mol sample of gas is at 300 K and 4.11 atm. What is the volume of the gas under these conditions? The sample is compressed to 6.0 atm at constant temperature, giving a volume of 3.99 L. Is this result consistent with Boyle’s law?

Q9.5.3

A 8.60 L tank of nitrogen gas at a pressure of 455 mmHg is connected to an empty tank with a volume of 5.35 L. What is the final pressure in the system after the valve connecting the two tanks is opened? Assume that the temperature is constant.

S9.5.3

281 mmHg

Q9.6.1

A spray can is used until it is empty except for the propellant gas, which has a pressure of 1344 torr at 23 °C. If the can is thrown into a fire (T = 475 °C), what will be the pressure in the hot can?

S9.6.1

3.40 × 10³ torr

Q9.6.2

A weather balloon contains 8.80 moles of helium at a pressure of 0.992 atm and a temperature of 25 °C at ground level. What is the volume of the balloon under these conditions?

Q9.6.3

The volume of an automobile air bag was 66.8 L when inflated at 25 °C with 77.8 g of nitrogen gas. What was the pressure in the bag in kPa?

Q9.6.4

How many moles of gaseous boron trifluoride, BF₃, are contained in a 4.3410-L bulb at 788.0 K if the pressure is 1.220 atm? How many grams of BF₃?

S9.6.4

8.190 × 10^–2 mol; 5.553 g

Q9.6.5

Iodine, I₂, is a solid at room temperature but sublimes (converts from a solid into a gas) when warmed. What is the temperature in a 73.3-mL bulb that contains 0.292 g of I₂ vapor at a pressure of 0.462 atm?

Q9.7.1

One method for preparing hydrogen gas is to pass HCl gas over hot aluminum; the other product of the reaction is AlCl₃. If you wanted to use this reaction to fill a balloon with a volume of 28,500 L at sea level and a temperature of 78°F, what mass of aluminum would you need? What volume of HCl at STP would you need? (STP means conditions of 1.00 atm and 273 K.)

S9.7.1

20.9 kg Al, 5.20 × 10⁴ L HCl

Q9.7.2

An 3.50 g sample of acetylene is burned in excess oxygen according to the following reaction:

2C2H2(g)+5O2(g)→4CO2(g)+2H2O(l)(10.E.2)(10.E.2)2C2H2(g)+5O2(g)→4CO2(g)+2H2O(l)

At STP, what volume of CO₂(g) is produced?

Q9.7.3

Calculate the density of ethylene (C₂H₄) under each set of conditions.

1. 7.8 g at 0.89 atm and 26°C
2. 6.3 mol at 102.6 kPa and 38°C
3. 9.8 g at 3.1 atm and −45°C

S9.7.3

1. 1.0 g/L
2. 1.1 g/L
3. 4.6 g/L

Q9.7.4

Determine the density of O₂ under each set of conditions.

1. 42 g at 1.1 atm and 25°C
2. 0.87 mol at 820 mmHg and 45°C
3. 16.7 g at 2.4 atm and 67°C

Q9.7.5

At 140°C, the pressure of a diatomic gas in a 3.0 L flask is 635 kPa. The mass of the gas is 88.7 g. What is the most likely identity of the gas?

Q9.7.6

What volume must a balloon have to hold 6.20 kg of H₂ for an ascent from sea level to an elevation of 20,320 ft, where the temperature is −37°C and the pressure is 369 mmHg?

Q9.7.7

What must be the volume of a balloon that can hold 313.0 g of helium gas and ascend from sea level to an elevation of 1.5 km, where the temperature is 10.0°C and the pressure is 635.4 mmHg?

S9.7.7

2174 L

Additional Exercises

1. What is the pressure in pascals if a force of 4.88 kN is pressed against an area of 235 cm²?
2. What is the pressure in pascals if a force of 3.44 × 10⁴ MN is pressed against an area of 1.09 km²?
3. What is the final temperature of a gas whose initial conditions are 667 mL, 822 torr, and 67°C and whose final volume and pressure are 1.334 L and 2.98 atm, respectively? Assume the amount remains constant.
4. What is the final pressure of a gas whose initial conditions are 1.407 L, 2.06 atm, and −67°C and whose final volume and temperature are 608 mL and 449 K, respectively? Assume the amount remains constant.
5. Propose a combined gas law that relates volume, pressure, and amount at constant temperature.
6. Propose a combined gas law that relates amount, pressure, and temperature at constant volume.
7. A sample of 6.022 × 10²³ particles of gas has a volume of 22.4 L at 0°C and a pressure of 1.000 atm. Although it may seem silly to contemplate, what volume would 1 particle of gas occupy?
8. One mole of liquid N₂ has a volume of 34.65 mL at −196°C. At that temperature, 1 mol of N₂ gas has a volume of 6.318 L if the pressure is 1.000 atm. What pressure is needed to compress the N₂ gas to 34.65 mL?
9. Use two values of R to determine the ratio between an atmosphere and a torr. Does the number make sense?
10. Use two values of R to determine how many joules are in a liter·atmosphere.
11. At an altitude of 40 km above the earth's surface, the atmospheric pressure is 5.00 torr, and the surrounding temperature is −20°C. If a weather balloon is filled with 1.000 mol of He at 760 torr and 22°C, what is its
    1. initial volume before ascent?
    2. final volume when it reaches 40 km in altitude? (Assume the pressure of the gas equals the surrounding pressure.)
12. If a balloon is filled with 1.000 mol of He at 760 torr and 22°C, what is its
    1. initial volume before ascent?
    2. final volume if it descends to the bottom of the Mariana Trench, where the surrounding temperature is 1.4°C and the pressure is 1,060 atm?
13. Air, a mixture of mostly N₂ and O₂, can be approximated as having a molar mass of 28.8 g/mol. What is the density of air at 1.00 atm and 22°C? (This is approximately sea level.)
14. Air, a mixture of mostly N₂ and O₂, can be approximated as having a molar mass of 28.8 g/mol. What is the density of air at 0.26 atm and −26°C? (This is approximately the atmospheric condition at the summit of Mount Everest.)
15. On the surface of Venus, the atmospheric pressure is 91.8 atm, and the temperature is 460°C. What is the density of CO₂ under these conditions? (The Venusian atmosphere is composed largely of CO₂.)
16. On the surface of Mars, the atmospheric pressure is 4.50 torr, and the temperature is −87°C. What is the density of CO₂ under these conditions? (The Martian atmosphere, similar to its Venusian counterpart, is composed largely of CO₂.)
17. HNO₃ reacts with iron metal according to

Fe(s) + 2HNO₃(aq) → Fe(NO₃)₂(aq) + H₂(g)

In a reaction vessel, 23.8 g of Fe are reacted but only 446 mL of H₂ are collected over water at 25°C and a pressure of 733 torr. What is the percent yield of the reaction?

18. NaHCO₃ is decomposed by heat according to

    2NaHCO₃(s) → Na₂CO₃(s) + H₂O(ℓ) + CO₂(g)

    If you start with 100.0 g of NaHCO₃ and collect 10.06 L of CO₂ over water at 20°C and 0.977 atm, what is the percent yield of the decomposition reaction?

Answers

1. 208,000 Pa
3. 1,874 K
5. \[\frac{P_{1}V_{1}}{n_{1}}=\frac{P_{2}V_{2}}{n_{2}}\nonumber \]
7. 3.72 × 10⁻²³ L
9. 1 atm = 760 torr
11. 1. 24.2 L
    2. 3155 L
13. 1.19 g/L
15. 67.2 g/L
17. 3.99%