Question

If the relative humidity of the air is 45% and its temperature is 23 degrees C, how many molecules of water are present in a room measureing 14m by 9m by 8.6m

Answer 1

relative hum = (actual vapor/satd vapor)*100
0.45 = (actual)/20.58 g/m^3
I found the 20.58 g/m^3 at this site.
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html

Solve for actual vapor and I find something like 9 g/m^3 but you need to do it more accurately.
The volume of the room is 14*9*8.6 = ??m^3 and that times 9 g/m^3 will give you xx grams H2O vapor. Convert that to moles ( moles = g/molar mass) and convert that to molecules H2O using Avogadro's number. Check my thinking.

Answer 2

How many air molecules are in a \rm 14.5 \times 12.0 \times 10.0~ft room? Assume atmospheric pressure of 1.00 \rm atm, a room temperature of 20.0 \rm {}^{\circ}C, and ideal behavior.

Volume conversion:There are 28.2 liters in one cubic foot.

Answer 3

How many air molecules are in a \rm 12.0 \times 12.0 \times 10.0~ft room? Assume atmospheric pressure of 1.00 \rm atm, a room temperature of 20.0 \rm {}^{\circ}C, and ideal behavior.

Volume conversion:There are 28.2 liters in one cubic foot