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Standardisation of Sodium Hydroxide(NaOH

• Sodium hydroxide (NaOH), as a solid and in solution, looses strength on exposure and its concentration needs to be determined or standardised by titration, using a hydrochloric acid (HCl) solution of a known concentration (0.1 M).
  
  

1, - Fill a 25mL or 50mL burette with 0.1M HCl soln. and zero or note the burette reading.

2. - Pipette 10mL of the approximate (~) 0.1M NaOH soln. into a 100mL conical (Erlenmeyer) flask and add 2-3 drops of phenolphthalein indicator solution.

3. - Titrate the NaOH soln. until a persistent pink end point is reached.

4. - The true molarity of your ~ 0.1M NaOH solution is calculated using the equation below -(see derivation and example)




				.... mL (Titre of 0.1 M HCL)		X			0.1M (HCl)
M (NaOH)		=		--------------------------------	----------------------------		--	-	---------------
					10 mL( ~ 0.1M NaOH)



5. - The above proceedure should be performed three (3) times, to check for precision, and the average result used.

Note: A 0.01M NaOH solution is prepared from a standardised 0.1M NaOH solution by dilution, utilising a volumetric flask (see NaOH solution preparation)