[diablo]

Hi folks,

my physical chemistry sucks, please help me with the following question :

A tank (Volume = 22,4l) contains 2mol H2 and 1mol N2 at 273K.
Calculate the partial pressures of the components and the total pressure of the mixture after the reaction with the assumption, that H2 completely reacts to NH3.
Solution: pN2 = 33,8kPa , pH2 = 0Pa, pNH3 = 135kPa and Ptotal= 169kPa

i tried it with the formula p = nRT/V, but it doesnt fit. I think there must be some relation to the reaction equation:
N2+3H20 = 2NH3, but i can't figure out what it is.

plz help 

[Yggdrasil]

Can you show your work so far?  It's hard to diagnose where you're having trouble without seeing what you have done?

[diablo]

i was going this way : 

For 1xN2 i need 3xH2 --> i'Ve got 2x H2 so thats 66,7% of the H2 --> now all my H2 is wasted.
Following this for N2 i need 100%-66,7% = 33,3% of N2.. with n= 0,33 i would get the right solution for pN2
(though im not sure if this is the right way how one should calculate this)

and i have no idea how to calculate this for pNH3....

[Yggdrasil]

Well from your balanced chemical reaction, you see that for every 3 mol of hydrogen used, you create 2 moles of ammonia.  Based on that ratio, how much ammonia will 2 mol of hydrogen create?

[diablo]

thx for your help - snack for you ! --> so i calculated (2/3)x2 ^^

greets diablo