Question on relative humidity

leena19

1. The problem statement, all variables and given/known data

Temperature of a closed room is 15 degree celsius (T₂₈₈).Relative humidity(RH)at 15degree celsius =60%
Find the RH when the temperature is 20 degrees.
S.V.P at 15 degrees celsius=12.67mmHg
SVP at 20 degree celsius = 17.36mmHg
(ans:45%)
2. Relevant equations



3. The attempt at a solution
RH= [Partial pressure at 15 degree celsius(P₁₅)/SVP at 15]*100%

P₁₅V = m₁rT₂₈₈ ----------(1)
p₂₀V=m₂rT₂₉₃ -----------(2)

I get the answer when i take m₁ as equal to m₂,but I don't understand why they should be equal.
Doesn't m,the mass of water vapour present in the room increase with temperature?

Thanx

tiny-tim

Hi leena19!
Always study the question …

it's a closed room!

Where would the extra mass come from?

leena19

Ah!OK.
Thank you very much!