# Finding pH given molarity and volume problem

1. Homework Statement
If you mix 200mL of a 1.8M HCl solution with 300mL of a 1.16M NaOH solution, what will be the pH of the solution?

3. The Attempt at a Solution
Well im really lost with this problem. Im pretty sure you need to convert each to moles.

.2L HCl x 1.8moles HCl
------------------
1L HCl

.3L NaOH x 1.16 moles NaOH
---------------------------
1L NaOH

HCl=.36moles

NaOH=.348moles

HCl + NaOH -> NaCl + H2O

not too sure where u go from there

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symbolipoint
Homework Helper
Gold Member
The acid and the base react 1:1, so which is in excess, and by how much?

is it .36-.348=.012 moles of HCl which = number of H+ ions?

pH=-log(.012) = 1.92?

or do u have to change moles of HCl back to molarity?

.012moles HCl
-------------
.5L total

=.024

pH=-log(.024)=1.62

symbolipoint
Homework Helper
Gold Member
HCl in aqueous solution is strongly ionized, or completely ionized for most practical purposes. For pH, you want the hydrogen ion CONCENTRATION AS MOLARITY...., and then find the negative logarithm.

Last edited:
yea so itd be 1.62 right?

Borek
Mentor
Yep, 1.62 it is.

chemisttree
Homework Helper
Gold Member
Welcome back, Borek! You were missed.

Borek
Mentor
Welcome back, Borek! You were missed.

I am planning to spend some time here now ;)