TO STANDARDIZE THE GIVEN HCl SOLUTION BY USING N/10 STANDARD Na2CO3 SOLUTION

OBJECTIVE:

TO STANDARDIZE THE GIVEN HCl SOLUTION BY USING N/10 STANDARD Na2CO3 SOLUTION AND EXPRESS THE CONCENTRATION IN TERMS OF MOLARITY, GRAM PER LITRE AND PERCENTAGE STRENGTH

APPARATUS REQUIRED

1. Conical flask
2. Pipette
3. Burette
4. Beaker
5. Glass tube

CHEMICALS REQUIRED

Sodium carbonate, hydrochloric acid, Methyl orange

THEORY

Standardization is the volumetric analysis in which the strength of the unknown solution is determined by treating it with a known volume of standard solution in the presence of a third substance with an indicator by measuring the volume of unknown solution consumed. In this standardisation, methyl orange is used as an indicator. The strength of the unknown solution is determined by using the law of chemical equivalence in which:

V_{1}N_{1}=V_{2}N_{2}\\
\text{where,}\\
\text{V1 = volume of base}\\
\text{N1 = Strength of base}\\
\text{V2 = volume of acid}\\
\text{N1 = Strength of acid}

Na_{2}CO_{3}+2HCl\rightarrow NaCl+H_{2}O+CO_{2}

PROCEDURE

All the apparatus was washed with water. The burette was rinsed with water followed by acid and filled up to the upper mark (zero). Burette is clamped into the stand. 10 ml solution of Na2CO3 was pipetted out and kept in the conical flask. 2-3 drops of methyl orange were added to the conical flask and the solution became yellow. Acid is gradually added to Na2CO3 solution from the burette a little at a time with constant shaking. At the endpoint, the solution became pink-coloured. The process was repeated until two concurrent readings were achieved.

OBSERVATION TABLE

CALCULATION

From the Normality equation,

\text{V1N1 = V2N2}\\
10\times \frac{1}{10} = 10.2\times N_{2}\\
N_{2}=0.09 N

Normality = 0.09 N

Molarity = Normality/n = 0.09/1 = 0.09 M

Gram per litre = Normality x eq. wt. = 0.09 x 36.5 = 3.285 gm/lit

Percentage strength = (gm/lit)/10 = 3.285/10 = 0.3285 %(w/v)

RESULT

Hence, the given acid solution (HCl) was standardised and its concentration was found to be 0.09N

CONCLUSION

The secondary standard solution can be standardised by using the primary standard solution.

PRECAUTIONS

1. Indicators should not be added in excess.
2. The conical flask should not be rinsed.
3. HCl should not be taken into the mouth while pipetting.