Determination of the Concentration of the Standard Solution

Titration Lab

Background: A titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask. A buret is used to deliver the second reactant to the flask and an indicator or pH Meter is used to detect the endpoint of the reaction.

Determination of the concentration of the standard solution:

For this lab, you will use NaOH as the standard solution (the solution that is placed in the buret & added to the solution of unknown concentration). The standard solution was prepared by adding 4.37 g NaOH(s) to a 1.0 liter volumetric flask that is filled to the line with de-ionized water to make 1.0 liter of NaOH solution.

What is the [NaOH(aq)]? (show work below)

Titration procedure:

Obtain an Erlenmeyer flask. Make certain it is clean & dried. To that flask add 50 ml of the HCl solution with the concentration you are trying to determine. While you are doing this, your lab partner should be making certain the buret is clean and filled with the NaOH standardized solution. The picture below may help explain the procedure.

Trial 1 Trial 2

Volume of acid used ______

Starting volume of NaOH ______

Ending volume of NaOH ______

Before beginning your titration, make certain to add the appropriate indicator. Because this lab involves a strong acid-strong base titration, the appropriate indicator is ______.

Begin the titration. For the first trial, you may want to add the standardized solution more quickly to give a rough idea as to what volume of base is needed to reach the endpoint. It is O.K. for the first trial to over shoot the endpoint of the titration. For the second trial, you will then know when to slow down the titration to obtain better results.

To determine the concentration of the acid solution, you can choose to use stoichiometry & a balanced equation or the following equation: NaVa = NbVb,

with N = normality & V = volume.

Determination of acid concentration:

Extra problems:

1) 30 mL of 0.10M NaOH neutralized 25.0mL of hydrochloric acid.
Determine the concentration of the acid.

2) 50mL of 0.2mol L-1 NaOH neutralized 20mL of sulfuric acid.
Determine the concentration of the acid.

3) 25.0mL of 0.05M Ba(OH)2 neutralized 40.0mL of nitric acid.
Determine the concentration of the acid.

4) What is the pH of a solution prepared by combining 35.0 ml 0.10 M HCl with 45.0 ml of 0.25 M NaOH?