# Question ae1f0

Mar 9, 2017

#### Answer:

$\text{0.176 moles gas}$

#### Explanation:

The thing to remember about STP conditions is that under these specific conditions for pressure and temperature, $1$ mole of any ideal gas occupies $\text{22.7 L}$ $\to$ this is known as the molar volume of a gas at STP.

Now, the old definition of STP conditions, i.e. a pressure of $\text{1 atm}$ and a temperature of ${0}^{\circ} \text{C}$, corresponds to a molar volume of ${\text{22.4 L mol}}^{- 1}$.

However, the current definition, i.e. a pressure of $\text{100 kPa}$ and a temperature of ${0}^{\circ} \text{C}$, corresponds to a molar volume of ${\text{22.7 mol L}}^{- 1}$.

So make sure to use the definition given to you by your instructor for the calculations!

Now, if $1$ mole occupies $\text{22.7 L}$ at STP, it follows that a $\text{4.00 L}$ cylinder kept under the same conditions will contain

$4.00 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{L"))) * "1 mole gas"/(22.7color(red)(cancel(color(black)("L")))) = color(darkgreen)(ul(color(black)("0.176 moles gas}}}}$

The answer is rounded to three sig figs, the number of sig figs you have for the volume of the cylinder.

If you want to use the old definition, simply set up the calculation like this

4.00 color(red)(cancel(color(black)("L"))) * "1 mole gas"/(22.4color(red)(cancel(color(black)("L")))) = ...#