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 base → proton acceptor
• H2O → will act as the weak acid → proton donor
Equilibrium reaction: (CH3)3NH+(aq) + H2O(l) ⇌ (CH3)3N(aq) + H3O+(aq)
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?
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