Pressure: Units, Formulas, and Conversions in GOB Chemistry

Pressure

Definition and SI Unit

Pressure is defined as the force exerted per unit area. It is a fundamental concept in chemistry, especially in the study of gases.

• SI Unit for Pressure: The SI unit is the pascal (Pa), named after the French mathematician Blaise Pascal.

• Formula:

$\text{Pressure} = \frac{\text{Force}}{\text{Area}}$

• Application: Pressure describes how a gas exerts force on the walls of its container due to molecular collisions.

Pressure and Volume Relationship

When the volume of a gas container changes while the amount of gas remains constant, the pressure will change inversely. This is a key principle in gas laws.

• If the volume increases, the pressure decreases.

• If the volume decreases, the pressure increases.

Example: If the same amount of gas molecules is transferred from a 5.0 L container to a 10.0 L container, the pressure will decrease.

Pressure Unit Conversions

In chemistry, several units are used to measure pressure. The most common are atm (atmosphere), mmHg (millimeters of mercury), and torr. Each unit has a specific value and can be converted to others.

• atm: Standard atmospheric pressure.

• mmHg: Pressure exerted by a column of mercury 1 millimeter high.

• torr: Equivalent to 1 mmHg.

Unit Name	Pressure Value	Unit Name	Pressure Value
Atmosphere (atm)	1	Pascals (Pa)	1.01325×105
Millimeters of Mercury (mmHg)	760	Kilopascal (kPa)	101.325
Torr	760	Pounds per square inch (psi)	14.696

Example: Pressure Conversion

To convert pressure from one unit to another, use the appropriate conversion factor.

• Example: The pressure in Denver, Colorado (elevation 5280 ft) averages about 24.9 inHg. Convert this pressure into mmHg and atm.

• Result: 0.832 atm

Additional info: Pressure conversions are essential in laboratory and clinical settings, where different instruments may use different units.