# A sample of neon has a volume of 75.8 at STP. How many moles are present?

Dec 20, 2016

3.38 moles are present

#### Explanation:

I am going to assume that you mean 75.8 L since there are no units associated with the volume you provided.

Because we are at standard temperature and pressure and are given only one set of conditions, we can to use the ideal gas law equation:

I should mention that the pressure does not always have units of atm, it depends on the units of pressure given in the gas constant.

List your known and unknown variables.

color(magenta)("Knowns:"
- Volume
- Temperature
- Pressure

color(blue)("Unknowns:"
Moles of neon

At STP, the temperature is 273K and the pressure is 1 atm.

Let's rearrange the equation to solve for n:

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

n = (1 cancel"atm" xx 75.8 cancel"L")/((0.0821 cancel"L"xxcancel"atm")/("mol"cancel"K")xx273cancel"K"

$n$ = 3.38 mol