In which of the following aqueous solutions does the weak acid exhibit the highest percentage ionization?

Question

A. 0.01 M HOCl (K_a = 3.5 × 10^-8)

B. 0.01 M HCN (K_a = 6.2 × 10^-10)

C. 0.01 M H₂SO₃ (K_a = 1.4 × 10^-2)

D. 0.01 M H₂CO₃ (K_a = 4.5 × 10^-7)

E. 0.01 M HC₃H₅O₂ (K_a = 1.3 × 10^-5)

Answer 1

The answer is C. H2SO3. It is the strongest acid so in aqueous solutions(mostly water i.e. pH 7) it would be mos ionized.

When considering ionization percentages a good place to start is with acids.

pKa denotes when 50% of the acid is Ionized. For example, COOH becomes COO-.

pH represents the power of proton/hydrogen. That is to say the concentration of protons/H+.

pH 1 has a higher concentration of protons ins solution than pH 5( it has to do with -logs so the relationship is inverse)

This means at a low pH there are more protons available so it is harder for a weak acid to give protons or Ionize. Though a strong acid like C and E would be able to.