Answer
Hydronium ion concentration:
$[H_3O^+] = 5.012 \times 10^{- 5}M$
Work Step by Step
$[H_3O^+] = 10^{-pH}$
$[H_3O^+] = 10^{- 4.3}$
$[H_3O^+] = 5.012 \times 10^{- 5}M$
- Solutions with pH < 7* are considered acidics.
* Which means $[H_3O^+] > 10^{-7}M$.