Determine the composition of the solution.
NH4Cl → breaks up in the solution
NH4Cl → NH4+ + Cl-
Equilibrium reaction: NH4+ + H2O ⇌ NH3 + H3O+
NH4+ → weak acid
NH3 → conjugate base
• The solution is composed of a weak acid and its conjugate base, therefore we have a buffer.
Calculate the pKa of the NH4+.
Ka = 5.555x10-10
pKa = 9.25
Determine the initial moles of the weak acid and conjugate base present.
Recall molarity is:
Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 M NH4CI with 100.0 mL of 0.20 M NH3. The Kb for NH3 is 1.8 x 10-5.
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