# Question e0eda

Jun 8, 2017

There are $\approx \text{ 200 moles}$ of air in the tank.

#### Explanation:

You would use the Ideal Gas Law:

$P V = n R T$

All of the variables you indicate in your question pertain to this equation, except for R, which is the gas constant, and which you might need to look up.

Known

$P = \text{20000 kPa}$

$V = \text{25 L}$

$T = \text{300 K}$

$R = \text{8.3144598 L kPa K"^(−1) "mol"^(−1)}$
https://en.wikipedia.org/wiki/Gas_constant

Unknown: moles: $n$ (moles)

Solution

Rearrange the ideal gas law equation to isolate $n$ on the left side. Insert your data and solve.

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

n=(20000color(red)cancel(color(black)("kPa"))xx25color(red)cancel(color(black)("L")))/(8.3144598 color(red)cancel(color(black)(" L")) color(red)cancel(color(black)(" kPa")) color(red)cancel(color(black)(" K"))^(−1) "mol"^(−1)xx300color(red)cancel(color(black)("K")))="200 mol air"# rounded to one sig fig