Remember that HCl is a strong acid will dissociate almost 100%
HCl + H₂O --> H₃O⁺ + Cl⁻
pH = -log[H₃O⁺]
pH = -log(0.045) = 1.35
(The rules for sig figs are that if you take the log of a number with x significant figures, then the result should have x significant decimal places.)
The pH is 1.35
