pH and pOH Video Lessons

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Concept:

Problem: Trimethylamine, (CH3)3N, is a weak base (Kb = 6.4 × 10–5) that hydrolyzes by the followingequilibrium: (CH3)3N + H2O → (CH3)3NH+ + OH– What is the pH of a 0.1 M solution of (CH 3)3NH+? (Enter pH to 2 decimal places; hundredth's.)

FREE Expert Solution
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FREE Expert Solution

For this problem, we know that Trimethylamine, (CH3)3N, is a weak base (Kb = 6.4 × 10–5) and hydrolyzes by the following equilibrium: 

(CH3)3N + H2O → (CH3)3NH+ + OH


We need to do these steps to solve for the pH of a 0.1 M solution of (CH3)3NH+ 

1. Write the equilibrium expression for (CH3)3NH+ in H2O 

2. Make an ICE chart to solve for [H3O+] (in M or moles/L) at equilibrium

  • Find Ka given Kb
  • Recall that: Ka × Kb = Kw

3. Solve for pH

Recall that pH is given by the equation:

pH =-logH3O+

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Problem Details

Trimethylamine, (CH3)3N, is a weak base (Kb = 6.4 × 10–5) that hydrolyzes by the following

equilibrium: (CH3)3N + H2O → (CH3)3NH+ + OH 

What is the pH of a 0.1 M solution of (CH 3)3NH+? (Enter pH to 2 decimal places; hundredth's.)

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the pH and pOH concept. You can view video lessons to learn pH and pOH. Or if you need more pH and pOH practice, you can also practice pH and pOH practice problems.

How long does this problem take to solve?

Our expert Chemistry tutor, Rae-Anne took 8 minutes and 27 seconds to solve this problem. You can follow their steps in the video explanation above.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Hanson's class at UCR.