Chemistry!!
posted by L .
Calculate the pH of 10.00 mL of 0.40 mol/L of hydrochloric acid.

pH = log (H^+)
HCl ionizes 100% so it is 0.4M. Substitute into the pH equation and solve. 
i did that, but the answer is wrong.

What did you get. SHOW YOUR WORK. That way I can find the error.
Your answer should have been 0.397 which I would round to 0.4 as a pH. By the way, the 10.00 mL has nothing to do with it (the concn is what counts) UNLESS the 10.00 mL was diluted to some final volume. But the problem does not say that. 
oh ok! i wasn't rounding, thank you.