What is the Ph for the solution made from 11.10mL of 0.278M HCL solution mixed with 70.90mL of 0.1300M ammonia solution? The pKa for NH4 is 9.241.

1 answer

mmols HCl = 11.1 x 0.278 = 3.0858
mmoles NH3 = 70.9 x 0.13 = 9.217
..........HCl + NH3 ==> NH4Cl
initi...3.0858..9.217....0
change-3.0858..-3.0858...+3.0858
equil....0.......6.131....3.0858
From the ICE chart you can see that you have a solution of NH3 (a weak base) and its salt (NH4Cl) which makes a buffer.
Use the Henderson-Hasselbalch equation to solve for pH. Check my arithmetic.