Which of the following is actually being measured when a vacuum is measured in microns?

• A. The volume of the gas in cubic centimeters (cm^3)
• B. The pressure of the gas in millimeters of mercury (mm Hg)
• C. The temperature of the gas in degrees Celsius (°C)
• D. The density of the gas in grams per liter (g/L)

Answer: (B)

Verified step by step guidance

1. Understand that a vacuum gauge measures how much the pressure inside a space is reduced compared to atmospheric pressure.
2. Recognize that 'microns' in vacuum measurement refers to microns of mercury, which is a unit of pressure, specifically a thousandth of a millimeter of mercury (mm Hg).
3. Recall that pressure is the force exerted by gas molecules per unit area, and vacuum gauges quantify this pressure to indicate how strong the vacuum is.
4. Note that volume, temperature, and density are different physical properties and are not directly measured by vacuum gauges.
5. Conclude that when a vacuum is measured in microns, it is actually the pressure of the gas being measured, expressed in very small units of mm Hg.