Finding pH given molarity and volume problem

[pmart491]

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?

The Attempt at a Solution

Well I am really lost with this problem. I am 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

 

[symbolipoint]

The acid and the base react 1:1, so which is in excess, and by how much?

 

[pmart491]

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

pH=-log(.012) = 1.92?

 

[pmart491]

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

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

=.024

pH=-log(.024)=1.62

 

[symbolipoint]

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.

 

[pmart491]

yea so itd be 1.62 right?

 

[Borek]

Yep, 1.62 it is.

 

[chemisttree]

Welcome back, Borek! You were missed.

 

[Borek]

Welcome back, Borek! You were missed.

I am planning to spend some time here now ;)