Stuck on chem lab

[yhelothar]

OK so I'm trying to finish up my lab at 5:45AM, and it asks me to determine the partial pressure of pure hydrogen with Dalton's Law of Partial Pressures.
I know that the partial pressure of water vapor at 21°C is 2.5kPa.
I figure I subtract that number from the total pressure to get the pressure of pure hydrogen. Unfortunately, I have no idea what the total pressure is.
Any ideas?

 

[virtueixi]

There should be a specific formula and/or constant for this, if I recall. Check your text/internet.

 

[yhelothar]

The forumla for dalton's law is P(total) = P(1) + P(2) +.....+P(n). I'm guessing there are two pressures total - water vapor and pure H2 gas. I have the water vapor. I just need the total pressure to get the pressure of the pure H2.

 

[Atomicus]

atmospheric pressure = 100kpa?

 

[yhelothar]

OK so the answer would be 100-2.5 or 97.5kPa?
Looks right to me..

 

[virtueixi]

That doesn't make sense to me. If the water's vapor pressure already exceeds atmospheric pressure, how can you compare it to 1 atm?

 

[yhelothar]

😕
Water pressure is 2.5kPa
atmospheric pressure at 1atm is 101.325kPa