To determine the strength of commercial hydrochloric acid (HCl), 10 ml of which have been dissolved per liter of the given solution

1. EXPERIMENT No.:-1
OBJECTIVE:
To determine the strength of commercial hydrochloric acid
(HCl), 10 ml of which have been dissolved per liter of the given
solution.

2. • Reagents Required:
• Sodium Carbonate (Na2CO3)
• Hydrochloric Acid (HCl)
• Distilled Water
• Indicator:
• Methyl orange
• End point: Yellow to Pink (acid solution in the burette).
Resonance Structure of Methyl Orange

3. HCl
Na2CO3 + Methyl Orange

4. Reactions Involved:
• Chemical Reactions:
HCl + Na2CO3 NaHCO3 + NaCl
NaHCO3 + HCl NaCl + H2O + CO2
Ionic Reactions:
CO3-2
+ H+
HCO3-
HCO3-
+ H+
H2O + CO2

5. Procedure
As the given solution of HCl is having 10 mL of commercial HCl (nearly 10 N) in 1000 mL. Hence, the
standard solution to be prepared should have nearly same normality.
1. Preparation of 0.1N solution of sodium carbonate: Dry 1.2-1.4 g of reagent grade Na2CO3 in a
weighing bottle at 150 – 160 °C for 2 hours. Cool and store the loosely stoppered bottle in the
desiccators. Weigh out nearly but accurately 1.325g of the dried Na2CO3, by method of difference.
Transfer quantitatively to the calibrated 250 mL volumetric flask. Add 40 – 50 mL of distilled water and
stir gently to dissolve the solid. Then make up the volume upto 250 mL and mix well. This is standard
Na2CO3 solution whose normality can be calculated by considering the amount transferred to volumetric
flask.
2. Titration: Rinse and fill the burette with given acid solution. Remove the air bubbles and set it at zero
mark. Pipette out 10 mL of the standard Na2CO3 solution into a 100 mL titration flask and add 1 drop of
methyl-orange. Titrate with the HCl to a sharp colour change i.e., till Pink colour is obtained. Repeat the
titration with every 10 mL of the Na2CO3 solution until three concordant readings are obtained.

6. Observations
1. Preparation of 0.1N solution of sodium carbonate:
• weight of the weighing bottle, w1 = ..................... g
• wt. of the weighing bottle + Na2CO3, w2 = .......................g
• wt. of the weighing bottle after transferring the salt,w3 = .......................g
• wt. of Na2CO3 transferred to volumetric flask, w4 = (w2 – w3) = ……………..g
• Volume of solution made = 250 mL

7. Observations
2. Titration:
• Volume of Na2CO3 solution taken for each titration = 10 mL
• Burette readings: Titration of Na2CO3 vs HCl
S.No. Initial Reading Final Reading Vol. of HCl used
1.
2.
3.
4.

8. Calculations
1. Preparation of 0.1N solution of sodium carbonate:
Normality of Na2CO3 solution =
(w2 – w3)
53
𝑋
1000
250

9. Calculations
2. Titration:
• To calculate Normality of dil HCl solution, apply normality equation:
=> NHCl X VHCL = NNa2CO3 X VNa2CO3
=> NHCl = NNa2CO3 X VNa2CO3 / VHCl
=> NHCl = NNa2CO3 X 10 / VHCl
• Strength of dil HCl solution = NHCl X 36.5 g/l (strength = Normality x Eq. wt.)
• Since, commercial HCl was diluted 100 times (10 mL in 1000 mL), the strength of
commercial HCl can be obtained by multiplying the strength of dil. HCl by 100.
Hence, strength of commercial HCl = NHCl x 36.5 x 100 g/l
• Result: Strength of commercial HCl is …………………. g/l