Estimate Mass H2O Vapor in 1 m^3 Air at +20°C

[Orbital]

Homework Statement

Estimate the mass of water vapor that is contained in $1 m^3$ of saturated air at a temperature of plus 20 degrees Celsius

2. The attempt at a solution
I looked up the saturation pressure for water vapor at the given temperature. Can I just use the ideal gas-law for the mass? i.e. is the solution as simple as
$$m_{H_2O} = \frac{P_{sat, H_2O}}{R_{H_2O}T}$$
or do I have to make another approach?

 

[lalbatros]

yes this looks right, but -as usual- be careful with the units

 

[Orbital]

Can you tell me why the phrasing of the problem is physically incorrect?