# If the absolute pressure of a gas is 550.280 kPa, what is its gage pressure?

Jan 3, 2015

4.43084 atm

#### Explanation:

The answer is 448.955 kPa, or 4.43084 atm.

The difference between absolute and gauge pressure is determined by their respective zero references.

The zero reference for absolute pressure is set against a perfect vacuum, while the zero reference for gauge pressure is set against ambient pressure.

As a result, absolute pressure is defined as the sum of the gauge pressure and the atmospheric pressure

${P}_{\text{absolute") = P_("gauge") + P_("atmospheric}}$

which makes gauge pressure equal to

${P}_{\text{gauge") = P_("absolute") - P_("atmospheric}}$

Since a value for the atmospheric pressure was not provided, let's assume its 1 atm, or 101.325 kPa. This makes the gauge pressure equal to

${P}_{\text{gauge}} = 550.280$ $\text{kPa} - 101.325$ $\text{kPa} = 448.955$ $\text{kPa}$, or

$448.955$ "kPa" * ("1 atm")/("101.325 kPa") = 4.43084 $\text{atm}$