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Finding pH given molarity and volume problem

  • Thread starter pmart491
  • Start date
19
0
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
 

Answers and Replies

symbolipoint
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The acid and the base react 1:1, so which is in excess, and by how much?
 
19
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is it .36-.348=.012 moles of HCl which = number of H+ ions?

pH=-log(.012) = 1.92?
 
19
0
or do u have to change moles of HCl back to molarity?

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

=.024

pH=-log(.024)=1.62
 
symbolipoint
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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:
19
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yea so itd be 1.62 right?
 
Borek
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Yep, 1.62 it is.
 
chemisttree
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Welcome back, Borek! You were missed.
 
Borek
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