# Question 5d74d

##### 1 Answer
May 27, 2015

You use the ideal gas law equation, which looks like this

$P V = n R T$, where

$P$ - the pressure of the gas;
$V$ - its volume;
$n$ - the number of moles of gas;
$R$ - the ideal gas constant, usually expressed in atm L/mol K;
$T$ - the temperature of the gas in Kelvin.

You know that your gas occupies a volume of 2 L at a pressure of 2 atm and a temperature of ${20}^{\circ} \text{C}$. Plug these values into the ideal gas lw equation and solve for $n$:

$P V = n R T \implies n = \frac{P V}{R T}$

n = (2cancel("atm") * 2cancel("L"))/(0.082(cancel("atm") * cancel("L"))/("mol" * cancel("K")) * (273.15 + 20)cancel("K")) = "0.1664 moles"#

SIDE NOTE Do not forget to convert the temperature to Kelvin! You do that by adding 273.15 to the value given in degrees Celsius, like I did above.

Rounded to one sig fig, the answer will be

$n = \textcolor{g r e e n}{\text{0.2 moles}}$