chem
posted by tomi on .
A sample of 7.80L of NH3(ammonia) gas at 22 degrees Celsius and 735torr is bubbled into a 0.350L solution of 0.400M HCl (hydrochloric acid).
The Kb value for NH3 is 1.8x105.
Assuming all the NH3 dissolves and that the volume of the solution remains at 0.350L , calculate the pH of the resulting solution.

Use PV = nRT to calculate moles NH3.
Use M x L to calculate moles HCl.
Write the equation to determine how much NH4Cl is formed and how much NH3 or HCl is left. I suspect NH3 is in excess; therefore, I suspect all of the HCl will be used and you will be left with NH4Cl and NH3 which is a buffered solution.
Use the HendersonHasselbach equation to solve for the pH. Post your work if you get stuck. 
thnaks...