In chemistry laboratory practice, an eudiometer is a graduated glass tube used to measure what property of gases during experiments?

Introduction / Context:
In experimental chemistry, different instruments are used to measure pressure, volume, temperature and other properties of gases. The eudiometer is a specialised piece of glassware seen in gas collection and gas analysis experiments. This question tests whether you know which property of gases an eudiometer is specifically designed to measure accurately in the laboratory.

Given Data / Assumptions:

• An eudiometer is a glass instrument used mainly in chemistry laboratories.
• It is usually a long, graduated tube closed at one end.
• The question asks which physical quantity it measures in routine use.
• The options include time, pressure and volume related choices.

Concept / Approach:
An eudiometer is basically a graduated tube that allows chemists to collect gases over water or another liquid and read off the volume directly from the scale. It can be inverted in a water trough so that gas displaces the liquid and the amount of gas collected corresponds to the volume indicated by the graduations. Although pressure conditions are important in calculations, the instrument itself is read as a volume measuring device. Therefore, we focus on volume of gases as the primary property measured.

Step-by-Step Solution:
Step 1: Recall the appearance of an eudiometer as a long, narrow, graduated glass tube used with a liquid reservoir. Step 2: Understand that graduations on such tubes are used to read the volume of the gas trapped inside. Step 3: Note that atmospheric pressure or vapour pressure may be considered when doing gas law calculations, but they are not directly read only from the eudiometer scale. Step 4: Conclude that the central quantity an eudiometer measures is the volume of gases.

Verification / Alternative check:
You may remember classic gas law experiments in which hydrogen or oxygen is generated in a reaction vessel and passed into an inverted tube standing in water. Students then read the gas volume from the eudiometer scale and later correct the readings for water vapour and atmospheric pressure. This practical memory reinforces that the first quantity obtained from a eudiometer is gas volume, not time or mass.

Why Other Options Are Wrong:

• Atmospheric pressure: Determined using a barometer or manometer, not read directly from the eudiometer scale.
• Time: Measured using stopwatches or clocks, unrelated to the eudiometer design.
• Vapour pressure: This is calculated or taken from tables; the eudiometer does not directly show vapour pressure.
• Mass of solids: Measured using balances, and not connected with a gas collecting tube.

Common Pitfalls:
Some learners confuse the eudiometer with pressure measuring instruments because gas experiments often involve both pressure and volume. Others simply guess atmospheric pressure because it sounds familiar. To avoid confusion, link the word eudiometer with reading gas volume in a tube, and remember that pressure measurement uses separate devices like barometers and manometers.

Final Answer:
An eudiometer is used to measure the volume of gases collected during chemical experiments.