What is the pH of a 5e-8 M HCl solution?

My attempt at solution:

I don't think you can -log that because that gives you a basic pH and adding a strong to water however little in amount shouldn't make pH basic.

ionization of water: H2O

H

^{+} + OH

^{-}Difference between H+ and OH- concentration must be 5e-8 since HCl is a strong acid so assume 100% dissociation into H+.

[H+] - [OH-] = 5e-8 ([OH-] = -5e-8+[H+])

Kw = 1e-14 = [H+][OH-]

I substituted [OH-] into Kw, 1e-14 = [H+][-5e-8+ [H+]]

[H+] = 1.28e-7

pH = 6.89 but apparently the answer is 7.00... how can it be completely neutral?

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A + B --> AB is 1st order with respect to A, zero order with respect to B. Initial concentration of A and B = both 0.100 M. After 1.5 hours, conc of B = 0.060 M. What is the specific rate constant?

ln 0.06 = -k(1.5 hr) + ln 0.100

k = 0.34 1/hr

but the answer is 0.61 1/hr, how do I get this?