CH 8 Mastering Chemistry

Consider a gas in a sealed, rigid container. Which of the following will increase if more gas is pumped into the container at constant temperature?

* the number of gas particles * the pressure of the gas * the collision frequency of the gas particles

Consider a gas in a sealed, rigid container. Which of the following will increase if the temperature of the gas is increased?

* the pressure of the gas * the kinetic energy of the gas particles *the speed of the gas particles *the collision force of the gas particles

What is the mass of a sample of O2 gas, which has a pressure of 740. mmHg, at a temperature of 25 °C, in a volume of 250. mL?

0.318 g

Gases are different from solids and liquids. In a sample of gas, the molecules are far apart. The gas molecules also move around and collide with each other as well as with the walls of the container. These collisions generate pressure. The pressure of a gas can be measured in different units. One convenient unit of measure is called the atmosphere (atm) because it is based on atmospheric pressure. At sea level, the average pressure is 1 atm. As you get higher in altitude, the pressure steadily drops until you leave the atmosphere, where the pressure is very close to 0 atm. The table below shows the different commonly used units of measuring gas pressure. Use this table in the pressure unit conversions.

1.15 atm = 874 mmHg

The temperature of a 500. mL sample of gas increases from 150. K to 350. K. What is the final volume of the sample of gas, if the pressure in the container is kept constant?

1170 mL

High-pressure liquid chromatography (HPLC) is a method used in chemistry and biochemistry to purify chemical substances. The pressures used in this procedure range from around 500 kilopascals (500,000 Pa) to about 60,000 kPa (60,000,000 Pa). It is often convenient to know the pressure in torr. If an HPLC procedure is running at a pressure of 2.95×108 Pa , what is its running pressure in torr?

2.95×108 Pa = 2.21×106 torr

The pressure in car tires is often measured in pounds per square inch (lb/in.2), with the recommended pressure being in the range of 25 to 45 lb/in.2. Suppose a tire has a pressure of 43.5 lb/in.2 . Convert 43.5 lb/in.2 to its equivalent in atmospheres.

43.5 lb/in.2 = 2.96 atm

A gas sample in a closed, expandable container of initial volume 5.00 L was allowed to warm from 25 °C to 35 °C, at constant moles and pressure. What was its new volume?

5.17 L

A gas at 5.00 atm pressure was stored in a tank during the winter at 5.0 C. During the summer, the temp in the storage area reached 40.0 C. What was pressure on gas then?

5.63 atm

A diver exhales a bubble with a volume of 250 mL at a pressure of 2.4 atm and a temperature of 15 °C. What is the volume of the bubble when it reaches the surface where the pressure is 1.0 atm and the temperature is 27 °C, if the moles are constant?

630 mL

The unit of 1 atmosphere used to describe the pressure of a gas is equal to

760 mmHg.

A balloon is filled with helium gas. The tempature is changed from 50 c to -150 C at contant pressure.

A (smallest size)

Carbon dioxide and water vapor together account for about 5% of the air we breathe.

False

During inspiration, we actually make use of 100% of the oxygen in the air we breathe.

False

If the volume of the original sample in Part A (P1 = 552 torr , V1 = 23.0 L ) changes to 50.0 L , without a change in the temperature or moles of gas molecules, what is the new pressure, P2?

P2 = 254 torr

Consider 5.00 L of a gas at 365 mmHg and 20. ∘C . If the container is compressed to 2.80 L and the temperature is increased to 38 ∘C , what is the new pressure, P2, inside the container? Assume no change in the amount of gas inside the cylinder.

P2 = 692 mmHg

The Ideal Gas Law is usually written as ________.

PV=nRT

A 12.0 L gas cylinder is filled with 8.80 moles of gas. The tank is stored at 51 ∘C . What is the pressure in the tank?

Ptank = 19.5 atm

A 14.0 L gas cylinder has been filled with 7.00 moles of gas. You measure the pressure to be 3.50 atm . What is the temperature inside the tank? Express your answer to three significant figures and include the appropriate units.

T = PV/nR Ttank = 85.3 K

Which of the following correctly describes the process of inspiration (air entering the lungs)?

The lungs expand, causing their internal pressure to decrease.

How would the partial pressure of oxygen in the blood change? Why does a person with severe emphysema sometimes use a portable oxygen tank?

The partial pressure of oxygen would be lower. Breathing a higher concentration of oxygen will help to raise the partial pressure of oxygen in the blood.

In the simulation, set the temperature of the sample gas to 304 K. Click on the "Run" button, and observe how the number of moles of the gas varies with an increase in the volume of the gas. Then, click on the "Reset" button, set the temperature of the sample gas to 504 K, and click on the "Run" button again. Observe the graph produced in the simulation, and select the correct options listed below.

The volume of the sample gas increases linearly with the number of moles. The volume of the gas doubles when the number of moles of the gas is doubled at the same temperature.

In deoxygenated blood, the partial pressure of carbon dioxide is greater than the partial pressure of oxygen left. ANSWER:

True

The volume of air in a person's lungs is 620. mL at a pressure of 760. mmHg. Inhalation occurs as the pressure in the lungs drops to 752 mmHg with no change in temperature or amount of gas. To what volume, in milliliters, did the lungs expand? Express the volume to three significant figures and include the appropriate units.

V = 627 mL When temperature and the amount of gas remain constant, pressure and volume have an inverse relationship according to Boyle's law: P1V1=P2V2. A slight decrease in pressure is accompanied by a slight increase in volume. The equation is rearranged to solve for V2 as follows: V2=P1V1P2=(760 mmHg)(620. mL)752 mmHg

A very flexible helium-filled balloon is released from the ground into the air at 20. ∘C. The initial volume of the balloon is 5.00 L, and the pressure is 760. mmHg. The balloon ascends to an altitude of 20 km, where the pressure is 76.0 mmHg and the temperature is −50. ∘C. What is the new volume, V2, of the balloon in liters, assuming it doesn't break or leak?

V2 = 38.1 L

A sample of a gas at room temperature occupies a volume of 23.0 L at a pressure of 552 torr . If the pressure changes to 2760 torr , with no change in the temperature or moles of gas, what is the new volume, V2? Express your answer with the appropriate units.

V2 = 4.60 L

Imagine that the gas shown in the simulation is an ideal gas such as helium. Notice that the final number of moles of gas is 1.00 mol for each experimental run. You can find the final volume of the gas using the y axis of the graph shown. Consider an experimental run at 273 K where the initial number of moles (n1) is actually 1.00 mol, and the final number of moles (n2) is 2.00 mol. Use the simulation to find the volume (V1) of 1.00 mol of helium at 273 K, and calculate the final volume (V2).

V2 = 44.8 L

A balloon is floating around outside your window. The temperature outside is 23 ∘C , and the air pressure is 0.800 atm . Your neighbor, who released the balloon, tells you that he filled it with 3.40 moles of gas. What is the volume of gas inside this balloon?

Vballoon = 103 L

what volume would a 0.250 mole sample of H₂ gas occupy, if it had a pressure of 1.70 atm and a temperature of 35°C?

a. 3.72 L

According to the kinetic theory of gases, particles of a gas

are very far apart.

As the temperature of a gas increases, the density of the gas will __________.

decrease

Use the words inspiration and expiration to describe the part of the breathing cycle that occurs as a result of each of the following. Drag the appropriate items to their respective bins. ANSWER:

inspiration occurs: * The volume of the thoracic cavity increases. expiration occurs: *The diaphragm relaxes, moving up into the thoracic cavity. * The pressure within the lungs is greater than that of the atmosphere.

An autoclave is used to sterilize surgical equipment because

it allows water to boil at temperatures above 100 °C

The boiling point of water at sea level is 100 °C. At higher altitudes, the boiling point of water will be

lower, because the atmospheric pressure is lower.

A 240. L kiln is used for vitrifying ceramics. It is currently operating at 815 ∘C , and the pressure is 0.9750 atm . How many moles of air molecules are within the confines of the kiln? Express your answer to three significant figures and include the appropriate units.

nair = 2.62 mol

Part A The force of gas particles against the walls of a container is called

pressure

According to Boyle's Law, the pressure of a gas increases as the volume decreases because

the gas particles strike the walls of the container more often.

Vapor pressure can be described as

the pressure exerted by a gas above the surface of its liquid.

At 4.00 L, an expandable vessel contains 0.864 mol of oxygen gas. How many liters of oxygen gas must be added at constant temperature and pressure if you need a total of 1.36 mol of oxygen gas in the vessel? Express the volume to three significant figures, and include the appropriate units.

volume that must be added = 2.30 L