What must be the molarity of an aqueous solution of trimethylamine, (CH3)3 N, if it has a PH=11.20?

Convert pH to pOH (pH + pOH = pKw = 14), then convert pOH to (OH^-) by pOH = -log(OH^-), then,

.....(CH3)3N + HOH ==> (CH3)3NH^+ + OH^-
equil...x................OH..........OH
where OH is the concn you found for OH^- above.
Kb = [(CH3)3NH^+][OH^-]/[(CH3)3N]
Substitute and solve for the denominator.

To find the molarity of an aqueous solution of trimethylamine, (CH3)3N, we need to make use of the pH value provided.

First, we need to find the concentration of hydroxide ions (OH-) in the solution. Since the pH is 11.20, we can use the equation pH = -log[H+], where [H+] represents the concentration of hydrogen ions.

pH = -log[H+]
11.20 = -log[H+]

Now, we know that in a basic solution, the concentration of hydroxide ions (OH-) and the concentration of hydrogen ions (H+) are related by the equation Kw = [H+][OH-]. The value of Kw at 25 degrees Celsius is 1.0 x 10^-14 mol^2/L^2.

So, to find the concentration of hydroxide ions (OH-), we rearrange the equation to get [OH-] = Kw/[H+].

At pH 11.20, the concentration of hydrogen ions ([H+]) is 10^(-11.20). Now we can calculate the concentration of hydroxide ions (OH-):

[OH-] = (1.0 x 10^-14 mol^2/L^2) / (10^(-11.20))

Calculating this, we get:

[OH-] = 6.3096 x 10^(-4) mol/L

Since trimethylamine is a weak base, it will react with water to form the conjugate acid (trimethylammonium ion) and hydroxide ions. The concentration of trimethylamine will be equal to the concentration of hydroxide ions.

Therefore, the molarity of the aqueous solution of trimethylamine is 6.3096 x 10^(-4) M.

To determine the molarity of an aqueous solution of trimethylamine, you need to understand the relationship between pH and pKa.

1. Determine the pKa value of trimethylamine (CH3)3N.
The pKa of trimethylamine is a measure of its acidity. In this case, trimethylamine acts as a base rather than an acid. The pKa for trimethylamine is 9.81.

2. Calculate the pOH value using the pH value.
Since pH + pOH = 14, we can calculate the pOH value as follows:
pOH = 14 - pH = 14 - 11.20 = 2.80

3. Determine the concentration of hydroxide ions ([OH-]).
The pOH value is related to the concentration of hydroxide ions using the formula:
pOH = -log [OH-]
Rearranging the formula, we get:
[OH-] = 10^(-pOH) = 10^(-2.80) = 6.31 x 10^(-3) M

4. Calculate the concentration of trimethylamine ([CH3)3N]).
Since (CH3)3N is a weak base, it reacts with water to produce hydroxide ions. The reaction can be represented as:
(CH3)3N + H2O ⇌ (CH3)3NH+ + OH-

In this reaction, the concentration of trimethylamine is equal to the concentration of hydroxide ions:
[CH3)3N] = [OH-] = 6.31 x 10^(-3) M

Therefore, the molarity of the aqueous solution of trimethylamine is 6.31 x 10^(-3) M.

0.19M