The only method of preparing a water soluble salt from a water soluble base (also called an alkali) is to use titration. This is where a known volume of base is reacted with an acid using an indicator. The indicator shows when the correct volume of acid has been added (i.e. when the reaction is fully complete) by changing colour.
Using a pipette fitted with a pipette filler, place 25 cm3 of the sodium hydroxide solution into a 100 cm3 conical flask. Add a few drops of an indicator, and note the indicator's name as well as the initial colour of the indicator in the alkali. Carefully fill a burette with the hydrochloric acid solution provided to above the zero mark, and run out the excess into a beaker, ensuring the space under the tap is full of acid.
Then run the acid from the burette into the conical flask slowly, making sure to swirl the flask during the addition, until the indicator changes colour i.e. all the alkali has reacted. Note the change in colour of the indicator. Note down the volume of acid used to neutralize the 25 cm3 of sodium hydroxide solution. Repeat this procedure a further two times, or until you have two results that agree closely with one-another ( within 0.5 cm3 of each other ).
Now repeat the procedure once more, but omit the indicator from the conical flask containing the sodium hydroxide solution. Add the correct volume of hydrochloric acid from the burette. This will give a clear colourless solution containing only sodium sulphate dissolved in water. Evaporate some of the liquid using a Bunsen burner and a crystallizing bowl, and leave to crystallize.
(i) Write up all your observations and results as they occur.
(ii) Write a full balanced chemical equation for this reaction and the reaction of sodium hydroxide with
| (a) sulphuric acid, |
| (b) nitric acid. |