# Worksheet: Gas Pressure Measurements

In this worksheet, we will practice describing the mechanisms of common gas pressure gauges and identifying sources of error in pressure measurements.

Q1:

A manometer is used to measure the pressure of a gas; the gas exerts a force on a column of liquid in the U-tube, causing it to fall at one end and rise at the other. Which of the following properties would make a liquid a bad choice for use in a manometer?

• AHigh density
• BLow toxicity
• CHigh thermal expansion
• DLow reactivity
• ELow vapor pressure

Q2:

How would the use of a volatile liquid affect the measurement of a gas using open-end manometers versus closed-end manometers?

• AIt will not affect the closed-end manometer readings but will increase the readings for the open-end manometer.
• BIt will not affect the open-end manometer readings but will increase the readings for the closed-end manometer.
• CIt will introduce a systematic error in both cases.
• DIt would have no effect in either case.

Q3:

The pressure of a sample of gas is measured with a closed-end manometer containing liquid mercury, as shown in the figure. The density of mercury is 13.6 g/mL and the acceleration due to gravity is 9.81 m/s2. What is the pressure of the gas sample?

Q4:

The pressure of a gas sample is measured at sea level using an open-end mercury manometer, as shown in the figure. The density of mercury is 13.6 g/mL and the acceleration due to gravity is 9.81 m/s2. Calculate the pressure of the gas sample in millimeters of mercury.

Q5:

The pressure of a sample of gas is measured at sea level with an open-end mercury manometer. Assuming atmospheric pressure is 760 mmHg, what is the pressure of the gas?

• A897 mmHg
• B555 mmHg
• C678 mmHg
• D623 mmHg
• E137 mmHg