# What is the volume occupied by one mole of helium at 0 C and 1 atm pressure?

##### 1 Answer

#### Explanation:

The conditions for temperature and pressure provided to you actually correspond to the * old* definition of

**STP**(Standard Pressure and Temperature).

Under these specific conditions, **mole** of any ideal gas occupies **molar volume of a gas**.

You can show that this is the case by using the **ideal gas law equation**, which looks like this

#color(blue)(ul(color(black)(PV = nRT)))#

Here

#P# is the pressure of the gas#V# is the volume it occupies#n# is the number of moles of gas present in the sample#R# is theuniversal gas constant, equal to#0.0821("atm L")/("mol K")# #T# is theabsolute temperatureof the gas

Rearrange the ideal gas law equation to

#PV = nRT implies V/n = (RT)/P#

Plug in your values to find -- **do not** forget to convert the temperature from *degrees Celsius* to *Kelvin*

#V/n = (0.0821 (color(red)(cancel(color(black)("atm"))) * "L")/("mol" * color(red)(cancel(color(black)("K")))) * (273.15 + 0)color(red)(cancel(color(black)("K"))))/(1color(red)(cancel(color(black)("atm"))))#

#V/n = "22.4 L mol"^(-1)#

This means that under these conditions for pressure and temperature, you get **for every mole** of an ideal gas present in a sample.

**SIDE NOTE** *STP conditions are currently defined as a pressure of*

*and a temperature of*

*Under these specific conditions, the molar volume of a gas is equal to*