What is the pH of a weak acid that is 0.2% ionized in a 0.2 M solution?

pH=3.40

Explanation:

For this question, we can start with the general ionization reaction of a general acid:

The acids can produce the hydronium ion (). If we can to calculate the pH we have to use the equation:

So, if we want to calculate the pH value we have to know the concentration of the hydronium ion. For this, we can check the percentage of ionization. If we have 0.2 % of ionization, we will have only  0.2 % of hydronium ions from the initial concentration. In other words, we can calculate the concentration of , if we do the 0.2% of the initial concentration, so:

With the concentration we can calculate the pH:

The pH value is 3.40

I hope it helps!