Question

g Calculate the pOH of a solution that results from mixing 23.3 mL of 0.16 M trimethylamine ((CH3)3N) with 44.1 mL of 0.15 M (CH3NH3Cl. The Kb value for (CH3)3N is 6.5 x 10-5.

Answer 1

Answer:

pOH = 5.961

Explanation:

To find the pH of a weak base we can use Henderson-Hasselbalch equation for weak bases:

pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]

Where pKb is -log Kb = 4.187 and [] could be taken as moles of each specie.

Moles (CH₃)₃NHCl:

0.0441L * (0.15mol/L) = 6.615x10⁻³moles

Moles (CH₃)₃N:

0.0233L * (0.16mol/L) = 3.728x10⁻³moles

And pOH is:

pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]

pOH = 4.187 + log [6.615x10⁻³moles] / [3.728x10⁻³moles]

pOH = 5.961