Which statement correctly describes how a manometer is used to measure the pressure of a gas in a container?

• A. A manometer determines the volume of a gas by the displacement of water in a graduated cylinder.
• B. A manometer directly measures the absolute pressure of a gas without reference to atmospheric pressure.
• C. A manometer measures the difference in mercury levels between two arms, which corresponds to the pressure of the gas relative to atmospheric pressure.
• D. A manometer is used to measure the temperature of a gas by observing the expansion of mercury.

Answer: (C)

Verified step by step guidance

1. Understand that a manometer is a device used to measure the pressure of a gas by comparing it to atmospheric pressure, not by measuring volume or temperature.
2. Recognize that a manometer typically consists of a U-shaped tube filled with mercury (or another liquid), where one side is connected to the gas container and the other is open to the atmosphere.
3. The difference in mercury levels between the two arms of the manometer indicates the pressure difference between the gas and the atmosphere.
4. Use the pressure difference to calculate the gas pressure relative to atmospheric pressure by applying the formula: \(P_{gas} = P_{atm} \pm \Delta h\), where \(\Delta h\) is the height difference of mercury columns.
5. Note that the manometer measures gauge pressure (pressure relative to atmospheric pressure), not absolute pressure, and it does not measure volume or temperature.