PRACTICAL-TITRATION OF STRONG ACID (0.1 N HCl) WITH STRONG BASE (0.1 N NaOH) BY POTENTIOMETRY

Object – Determination of Normality by electrochemical methods [Potentiometric titration of strong acid (0.1 N HCl) against strong base (0.1 N NaOH)]

Reference – Rao G.D., Practical pharmaceutical analysis, Birla publications Pvt. Ltd., Delhi, II edition, 2007-08, 136

Materials required-

Chemicals – 0.1 N HCl, 0.1 N NaOH, Distill water

Glassware & Apparatus/Instumentation – Potentiometer or PH meter, Magnetic stirrer, burette, beaker, pipette.

Theory – Potentiometric determination of the end point depends on the fact that the potential cross the two electrodes (reference and indicator) immersed in the solution changes sharply at the equivalence or end point. This change is similar to the color change by an indicator in usual method. But the potentiometric method is more accurate. These ti0trations are useful when no suitable color indicators are available. Equivalence point can be accurately found out after plotting normal plot (i.e. volume of Titrant Vs potential).

Procedure –

  1. In a 250 ml beaker, 10 ml of 0.1 N HCl was taken and then 100 ml of water was added to it, so that the electrodes can dip properly.
  2. The beaker was now kept on magnetic stirrer.
  3. Potential was noted down without adding alkali.
  4. Now potential was noted down with adding known volume of 0.1 N NaOH Solution.
  5. Now from the obtained data, a graph was plotted between volume of titrant and potential.
  6. From the graph end point was calculated.

Observation –

S.NO. VOLUME OF TITRANT ADDED POTENTIAL
1 1 ML
2 1 ML
3 1 ML
4 1 ML
5 1 ML
6 1 ML
7 1 ML
8 1 ML
9 1 ML
10 1 ML

 

Result – The end point in the titration of strong acid (0.1 N HCl) with strong base (0.1 N NaOH) was found ……………………….

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