Finding pH given molarity and volume problem

AI Thread Summary
To find the pH of a solution created by mixing 200 mL of 1.8M HCl with 300 mL of 1.16M NaOH, the moles of each reactant must first be calculated. The calculations yield 0.36 moles of HCl and 0.348 moles of NaOH, indicating that HCl is in slight excess by 0.012 moles. This excess corresponds to the concentration of hydrogen ions, which is calculated by dividing the excess moles by the total volume of the solution (500 mL). The resulting hydrogen ion concentration is 0.024 M, leading to a pH of 1.62. The final pH confirms the strong ionization of HCl in the solution.
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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
 
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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
 
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?
 
Yep, 1.62 it is.
 
Welcome back, Borek! You were missed.
 
chemisttree said:
Welcome back, Borek! You were missed.

:blushing:

I am planning to spend some time here now ;)
 
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