# What is the volume of 19.87 mol of ammonium chloride (NH_4Cl) at STP?

Jun 8, 2016

445.3 L of $N {H}_{4} C l$

#### Explanation:

Since we are at STP, we would use the ideal gas law equation
$P \times V = n \times R \times T$.

• P represents pressure (must have units of atm)
• V represents volume (must have units of liters)
• n represents the number of moles
• R is the proportionality constant (has units of $\frac{L \times a t m}{m o l \times K}$)
• T represents the temperature, which must be in Kelvins.

Now what you want to do is list your known and unknown variables. Our only unknown is the volume of $N {H}_{4} C l$. Our known variables are P,n,R, and T.

Since we are at STP, the temperature is 273K and the pressure is 1 atm. We are given moles and the proportionality constant, R, is equal to 0.0821 $\frac{L \times a t m}{m o l \times K}$
Now all we have to do is rearrange the equation and solve for V like so:
$V = \frac{n \times R \times T}{P}$
$V = \frac{19.87 m o l \times 0.0821 \frac{L \times a t m}{m o l \times K} \times \left(273 K\right)}{1 a t m}$
$V = 445.3 L$