EXPERIMENT :1
Aim: Determination of the concentration (strength) of a given sodium hydroxide solution by titrating it against a standard solution (M/10) of oxalic acid.

Material Required: Burette, Pipette,  Conical flask ,  Burette stand, Funnel , Measuring flask , • Oxalic acid, Sodium hydroxide solution, Phenolphthalein indicator
Theory : In the titration of a strong acid with a strong base, the amount of acid and base becomes chemically equivalent at the end point and the chemical reaction is called neutralization reaction. Near the end point there is a sudden change in the pH of the solution. If after end point even a small amount of base/acid is added the solution would become slightly alkaline or acidic respectively. In the titration between oxalic acid (weak acid) and sodium hydroxide (strong base), following reaction takes place: In this titration phenolphthalein (HPh) is used as an indicator. The concentration of unknown solution is calculated in g/L. Molarity of the solution can be calculated by using the formula
 a1 M1 V1 = a2 M2 V2
 where a1 , M1, V1 are respectively basicity, molarity and volume of acid used and a2, M2 and V2 are acidity, molarity and volume respectively of base used in the titration.

Sl. No.	Volume of oxalic acid solution taken in conical flask each time V1mLBurette reading	Burette Initial reading (x)	Burette Final reading(y)	Volume of sodium hydroxide solution used V2 mL = (y–x) mL	Average
1	20 ml	0.0	4.2	4.2
2	20 ml	4.2	8.1	4.1
3	20 ml	8.1	11.4	3.3	3.8

Calculations:
 Molarity of NaOH solution can be calculated by using the equation: Oxalic acid Sodium hydroxide
2M1V1(Oxalic acid) = a2 M2V2(NaOH) 
2 *M/10  * 20  = M2 * 3.8
M2= 1.05 M



 Concentration (strength) in g/L = Molarity×Molar mass
                                                     = 1.05 * 40
                                                = 42.10 g/L
Result Concentration of NaOH solution is 42.10 g/L
Precautions (a) Always rinse the burette with the solution, which is to be taken in it.
(b) Remove the air gap if any, from the burette before titrating the solution. Make sure that the nozzle of burette is also filled.
 (c) Never forget to remove the funnel from the burette before noting the readings of the burette and ensure that no drop is hanging from the nozzle of the burette.
(d) Always read the lower meniscus for all transparent solutions and upper meniscus for coloured solutions.
(e) To note the burette readings, place the eye exactly at the level of the meniscus.
(f) Never hold the pipette at the bulb.
(g) Never use the pipette and burette with a broken nozzle.

What questions can be asked from the above given experiment in chemistry viva?