Calculate the ph of an aqueous solution that is 0.045 m in hcl (aq) at 25°c

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