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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: trinhn812 on January 02, 2008, 08:17:44 PM

Title: Trick Question? (Equilibrium problem)
Post by: trinhn812 on January 02, 2008, 08:17:44 PM

For the reaction    NH3(g) + H2S(g) ↔ NH4HS(s)   

K = 400. at 35.0°C.  If 2.00 mol each of NH3, H2S, and NH4HS are placed in a 5.00-L vessel, what mass of NH4HS will be present at equilibrium?  What is the pressure of H2S at equilibrium?



Since the product is a solid, wouldn't the equation be
K = 0/ [NH3] [ H2S].  Hence I wouldnt have to finish the problem?

or would it just be [NH4HS]/ [NH3] [ H2S]?

Title: Re: Trick Question? (Equilibrium problem)
Post by: LQ43 on January 02, 2008, 09:26:44 PM

Sorry, can't get out of doing the problem

the concentration of a pure solid or liquid in an equilibrium is constant at a given temperature and so becomes part of K,

K = 1/ ([NH3][H2S])

Title: Re: Trick Question? (Equilibrium problem)
Post by: yosh on January 02, 2008, 10:19:34 PM

First use the ideal gas law to find the total pressures of the gases.  Then use Dalton's law to find out the pressure of H2S.

Title: Re: Trick Question? (Equilibrium problem)
Post by: Borek on January 03, 2008, 03:58:58 AM

Quote from: yosh on January 02, 2008, 10:19:34 PM

First use the ideal gas law to find the total pressures of the gases.  Then use Dalton's law to find out the pressure of H2S.

No. You have to account for the reaction taking place. LQ43 already hinted in the right direction (no surprise here ;) ).

Title: Re: Trick Question? (Equilibrium problem)
Post by: LQ43 on January 03, 2008, 09:16:43 PM

 thanks Borek! :)