Problem: What is the pH of 0.67 M trimethylammonium iodide, (CH3)3NHI? Enter your answer with two decimal places.The Kb of trimethylamine, (CH3)3N, is 6.3 x 10-5.

FREE Expert Solution

We are being asked to calculate the pH for a 0.67 M solution of (CH3)3NHI. 


(CH3)3NHI is the salt form of the conjugate acid of (CH3)3N



(CH3)3NHI disociates as: 

(CH3)3NHI (aq) → I-(aq) + (CH3)3NH+(aq)


The base dissociation goes as: 

(CH3)3N(aq) + H2O(l) →(CH3)3NH+(aq) + OH-(aq)


Since we’re dealing with a weak acid we will have to create an ICE chart to determine the equilibrium concentration of each species:

 (CH3)3NHI(aq)  weak baseproton acceptor
H2O → will act as the weak acidproton donor


Equilibrium reaction:        (CH3)3NH+(aq)  + H2O(l)    (CH3)3N(aq) + H3O+(aq)


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Problem Details

What is the pH of 0.67 M trimethylammonium iodide, (CH3)3NHI? Enter your answer with two decimal places.

The Kb of trimethylamine, (CH3)3N, is 6.3 x 10-5.

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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 Weak Acids concept. If you need more Weak Acids practice, you can also practice Weak Acids practice problems.