# Suppose that 7.47 x 10^-3mol of hydrogen gas occupies a 335 mL container at -91°C what is the pressure (in torr)? i know the answer is 253 .. but idk how to work it? someone please help me?

##### 1 Answer

Use the ideal gas law equation to find the pressure of the sample.

#### Explanation:

You know that your sample of hydrogen occupies a volume of

Since you know number of moles, volume, and temperature, you can use the ideal gas law equation to determine the pressure of the sample.

#PV = nRT" "# , where

*universal gas constant*, usually given as

So, rearrange the ideal gas law equation to solve for

#P = (nRT)/V#

Plug in your values and find *liters* and the temperature in *Kelvin*

#P = (7.47 * 10^(-3)color(red)(cancel(color(black)("moles"))) * 0.082("atm" * color(red)(cancel(color(black)("L"))))/(color(red)(cancel(color(black)("mol"))) * color(red)(cancel(color(black)("K")))) * (273.15 - 91)color(red)(cancel(color(black)("K"))))/(335 * 10^(-3)color(red)(cancel(color(black)("L"))))#

#P = "0.33306 atm"#

To get the pressure in *torr*, you need to use the conversion factor

#"1 atm " = " 760 torr"#

This will get you

#0.33306color(red)(cancel(color(black)("atm"))) * "760 torr"/(1color(red)(cancel(color(black)("atm")))) = color(green)("253 torr")#

Here are some cool videos to help you get comfortable with the ideal gas law equation