Question

Calculate the ionization constant for the following acids or bases from the ionization constant of its conjugate base or conjugate acid: Keep your answer to 2 significant figures (CH3)3NH+

Answer 1

Answer:

7.41 × 10⁻⁵

Explanation:

Let's consider the basic dissociation reaction of trimethylamine (CH₃)N).

(CH₃)N + H₂O = (CH₃)NH⁺ + OH⁻

According to Brönsted-Lowry, in this reaction (CH₃)N is a base and (CH₃)NH⁺ is its conjugate acid. The pKb for (CH₃)N is 9.87. We can calculate the pKa of (CH₃)NH⁺ using the following expression.

pKa + pKb = 14

pKa = 14 - pKb = 14 - 9.87 = 4.13

Then, we can calculate the acid dissociation constant for (CH₃)NH⁺ using the following expression.

pKa = -log Ka

Ka = antilog - pKa = antilog -4.13 = 7.41 × 10⁻⁵