Answer to Question #148236 in General Chemistry for Alberto

Question

Determine the pH of a solution consisting of 0.15 M NH4Cl and 1.5 M NH3. The Kb of NH3 is 1.8x10-5
.

Answer 1

pH= ?

[NH₄Cl]= 0.15M

[NH₃]= 1.5M

K_b= 1.8 x 10^-5

Now,

pK_b= -logK_b

pK_b= -log(1.8x10^-5)

pK_b= 4.745

We can now calculate pOH using Henderson Hasselbalch equation

pOH= pK_b + log[salt]/[Acid]

pOH= 4.745 + log(0.15/1.5)

pOH= 3.745

We can now find the pH

pH + pOH= 14

pH= 14 - pOH

pH= 14 - 3.745

pH= 10.26