Question

For a solution that is 0.170 M NH3 and 0.110 M NH4Cl calculate the following A) [OH-] B) [NH+4] C) [Cl-] D) [H3O+]

Answer 1

You have an ammonia/ammonium ion buffer solution. Use the Henderson-Hasselbalch equation for base hydrolysis.

Parts B and C:
[NH4^+] = [Cl^-] = 0.110 M = same as NH4Cl concentration. This is given in the problem.
NH4Cl is dissolved and dissociates in solution into NH4^+ and Cl^- ions

pOH = pKb + log[NH4^+]/[NH3]

pKb = 4.75 for NH₃

Part A:
pOH = pKb + log[NH4+]/[NH3] = 4.75 + log(0.11)/(0.170) = 4.56
[OH^-] = 10^-pOH = 10^-4.56 = 2.75x10^-5 M

Part d:
[H^+][OH^-] = 1x10^-14
[H^+] = (1x10^-14) / (2.75x10^-5) = 3.64x10^-10 M

Hope this helps