The net result of the displacement titration between the tetraborate ion with hydrochloric acid is
The boric acid so formed is a weak monoprotic acid (Ka = 6.4 x 10^ -10). Therefore it cannot be directly titrated with standard alkali. However by the addition of certain organic polyhydroxy compounds it is converted to a much stronger acid which can be titrated using phenolphthalein. This is due to the complex formation between hydrated borate ion and 1,2 or 1,3 diols.
If you can't see the image clearly please click on it.
I. Calculate the mean and the standard deviation of your reading.
II. Using the mean value calculate the concentration of the HCl acid.
III. Draw the titration curve.
IV. What are the advantages of using borax as a primary standard to standardize strong acids?
Introduce 2gof Glucose, swirling gently to dissolve. Add 2 drops of phenolphthalein and titrate with the NaOH provided. When the first permanent pink color is produced add further 0.5g glucose. If the pink color disappears, titrate with more NaOH until the pink color reappears.
Standardize the NaOH against the HCl using phenolphthalein indicator.
I. Calculate the concentration of NaOH,
a) From the titrations against HCl and
b) From the titrations in which glucose was added to the borax
II. Explain the important stages of the above procedure.
III. Write down the titration methods to determine concentrations of each component in a mixture of,
a) Boric acid and strong acid
b) Sodium tetraborate and boric acid