Question

Calcaulate the pH after 10.0 mL of 0.40 M HCl is added to 20.0 mL of 0.50 M NaOH.


I wasn't sure on how to start this problem. I tried to break the HCl and NaOH apart then I set up ICE for each but I did get the wrong answer of 13.70.

a. 0.40
b. 13.70
c. 13.30
d. 0.30

Answer 1

First you must recognize that HCl is a strong acid and NaOH is a strong base; therefore, the salt produced (NaCl) will not hydrolyze and the solution will be neutral IF the HCl and NaOH EXACTLY neutralize each other. So what you need to do is to calculate the moles HCl and the moles NaOH, see which is in excess and calculate H^+ or OH^- from that. If neither is in excess, the solution will be neutral at pH = 7.