Periodic acid, HIO₄, is an important oxidizing agent and a moderately strong acid. In a 0.10 M solution, the [H⁺] = 3.8 x 10⁻² mol/L. Calculate the Ka for periodic acid.
a) 1.9 x 10⁻²
b) 2.6 x 10⁻²
c) 4.2 x 10⁻³
d) 5.3 x 10⁻⁴