Determining the Concentration of an Aqueous Solution of Sodium Hydroxide, Naoh. Essay Example

Method 1

Titration

• For the titration, it is necessary to dilute the Sodium Hydroxide so that it is an easier concentration to titrate. Using a 25cm3 pipette, washed out with some of the NaOH solution, transfer 25cm3 of the solution to a 250 cm3 volumetric flask, and fill to the line with distilled water. The alkali will now have a concentration of 0. 1 mol dm-3.
• In the titration, the NaOH will be in the burette, and will be titrated into HCl in a conical flask: NaOH (aq) + HCl (aq) ? NaCl (aq) + H2O (l) The reaction is 1:1 between NaOH and HCl, so a solution of 0. 2 mol dm-3 should be used.
• Rinse a 25cm3 pipette out with some of this solution, and then transfer 25cm3 of it to a clean conical flask.
• Ad
  ...

  d 3 drops of phenolphthalein.

• Wash a burette with some of the diluted alkali and then fill the burette to the top of the graduations.
• Titrate the alkali into the acid until the indicator in the flask has turned a pink colour.
• Repeat the process until two titres are obtained within 0. 1cm3 of each other, as well as a rough titre. e. g. Average titre = 24. 0 cm3. Moles of acid used = 5x10-3 Acid neutralised by 24. 80 cm3 NaOH Therefore concentration of NaOH = (5x10-3 x 1000)/ 24. 8 =0. 2016129… Diluted by factor of 10, so: 0. 2016129…x10 = 2. 01 mol dm-3. Method 2- ? H of neutralisation
• Transfer 25cm3 of NaOH into a polystyrene cup with a lid, and put the cup into a plastic beaker.
• Take the temperature of the