pH scale is used to determine how acidic or basic a solution is.
pH can be calculated as follows
pH = - log [H₃O⁺]
since pH is known we can calculate [H₃O⁺]
[H₃O⁺] = antilog(-pH)
pH = 4.282
[H₃O⁺] = - antilog (-4.282)
[H₃O⁺] = 5.22 x 10⁻⁵ M
concentration of hydronium ions is 5.22 x 10⁻⁵ M