CHE 106 Lecture Notes - Lecture 40: Pressure Measurement, Barometer, Torr

1. Convert 0.955 atm to kPa:

A) 96.8 kPa

B) 96.8 x 103 kPa

C) 96.765 kPa

D) 96.77 kPa

2. Consider a manometer where the height of the mercury column is 32 mm higher on the atmospheric side than on the gas side. If the laboratory pressure is 1 atm, what is the pressure of the gas in the manometer?

A) 792 torr

B) 732 torr

C) 760 torr

D) 728 torr

E) 766 torr

F) 97000 Pa

3. If a balloon is cooled, the volume _______ while the pressure inside the balloon _________

A) increases, remains the same

B) decreases, increases

C) decreases, remains the same

D) decreases, decreases

4. The following are commonly observed properties of gases (There may be more than one answer):

A) gases do not exert pressure on surroundings

B) gases experience a "memory" effect and take on the shape of previous containers

C) gases have no definite shape of their own

D) gases cannot be compressed

E) a gas completely fills the container it occupies

F) gases exert pressure on their surroundings

G) gases are highly compressible

Thank you!

To understand several methods of measuring gas pressure. Gases exert a measurable pressure (P) on the walls of their container. The SI unit for pressure is the pascal (Pa). Other pressure units frequently used in chemistry are millimeters of mercury (mmHg) and atmospheres (atm). You can convert between units of pressure using conversion factors such as those indicated below. 1 atm=760 mmHg=101,325 Pa

Part A

On a rainy day, a barometer reads 737 mmHg . Convert this value to atmospheres.

Express your answer numerically in atmospheres

Part B

A closed container is filled with oxygen. The pressure in the container is 445 kPa . What is the pressure in millimeters of mercury?

Express the pressure numerically in millimeters of mercury.

Part C

What is the pressure (in atmospheres) of the gas inside the container connected to an open-end, mercury-filled manometer as shown in the picture? (Figure 1) The atmospheric pressure is 0.95 atm.

Express your answer numerically in atmospheres.

Converting between Units of Pressure 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. Unit Abbreviation 1 atm equivalent atmosphere atm 1.00 atm (exact) millimeters of mercury mmHg 760 mmHg torr torr 760 torr inches of mercury in.Hg 29.9 in.Hg pounds per square inch (psi) lb/in.2 14.7 lb/in.2 pascal Pa 101,325 Pa.

Part C

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 5.81×10⁸ Pa , what is its running pressure in torr?

Express the pressure numerically in torr.