# How do you determine the density of water vapor at different temperatures?

Jun 18, 2018

see below

#### Explanation:

you can consider water vapor as an ideal gas , so you can write the ideal gases law
$P \times V = n \times R \times T$
where
P= pressure
V= volum
n= number of mol (n= mass in g/ MM)
R= universal costant of ideal gases
T= temperatur in K
so you can write the ideal gases law in this way
$P \times V = \left(\frac{m}{M M}\right) \times R \times T$
density is mass divided volume $d = \frac{m}{V}$
and riarranged the equation you have
$d = \frac{m}{V} = \frac{P \times M M}{R \times T}$
where you can see that increasing temperature, d decreases.
Moreover as the MM of water (18g/mol) is less than MM of air (about 29 g/mol), vapor has a less density tthan air