How does one go about doing a titration experiment involving a known conc. & volume of NaOH to determine the conc. of HCL needed?Basically the aim of the investigation is to determine the...

How does one go about doing a titration experiment involving a known conc. & volume of NaOH to determine the conc. of HCL needed?

Basically the aim of the investigation is to determine the concentration of HCL (hydrochloric acid) using a known volume and concentration of NaOH (sodium hydroxide). I have absolutely no idea what titration is, the teacher has told us to come prepared into class as we would be doing a practical on it. Can I have a step by step procedure and a little bit of an explanation as I am a bit lost? Volume(s) and concentration(s) of NaOH would be helpful.

 

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jerichorayel | College Teacher | (Level 2) Senior Educator

Posted on

Hello!

 

Titration is a quantitative chemical process in determining the concentration (or amount) of unknown substance using an identified reagent.

In short, we can simply show it as:

solution 1 of a known concentration is added to solution 2 of unknown concentration. In general, we use an indicator to know if we already reach the end point (it will change color)

If the solution changes in color we assume two things:

1. the end point is reached

2. the amount of solution 1 is stoichiometrically equal to the amount of solution 2.

in your case we can say that:

moles of HCl = moles NaOH   

*remember that we know the concentration and volume of NaOH.

 

-------------let me give you an example-------------------

 

50 mL of unknown concentration of HCl is titrated with 0.5 moles/L NaOH. When the titration reached the endpoint the volume of NaOH consumed is 45.57mL. Find the concentration of HCl.

We know from the above discussion that at endpoint:

moles HCl = moles NaOH

how do we get the moles of NaOH?

remember molarity?

             Molarity = moles NaOH /volume of solution (in liters)

             **by arranging the formula we have**

 

             moles NaOH = Molarity x volume 

                               = 0.5 moles/L x (45.57/1000)L

                               = 0.022785moles NaOH

 

             **we divided 45.57 by 1000 because 

                 1000mL = 1 L**

 

So we have 0.022785moles NaOH which is equal to moles HCl.

Therefore:

moles HCl = 0.022785

 

now we can calculate the molarity of HCl

(molarity is the concentration)

 

molarity HCl = moles HCl/volume HCl solution

                  = 0.022785 moles HCl / (50/1000)L

                  = 0.4557 moles/L

 

 

 

Hope this helps :)

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