Estimation of Sodium Carbonate and Sodium Bicarbonate in a Mixture

AIM OF THE EXPERIMENT

• Objective: Estimation of sodium carbonate ($Na_2CO_3$) and sodium bicarbonate ($NaHCO_3$) present together in a mixture.
• Experiment Number: 03
• Date of Experiment: 16.04.2026
• Page References: Pages 08 through 13.

PRINCIPLE AND CHEMICAL REACTIONS

• General Principle: The reaction between sodium carbonate ($Na_2CO_3$) and hydrochloric acid ($HCl$) occurs in two distinct stages. The titration for the estimation of sodium carbonate and sodium bicarbonate is conducted in two stages because of this stepwise reaction.
• Reaction Stages for Sodium Carbonate:
  • Stage 1: Hydrochloric acid reacts with sodium carbonate to produce sodium bicarbonate and sodium chloride.
    • Equation: $Na_2CO_3 + HCl \rightarrow NaHCO_3 + NaCl$
  • Stage 2: The sodium bicarbonate (both original and that formed in stage 1) reacts with hydrochloric acid to produce sodium chloride, water, and carbon dioxide.
    • Equation: $NaHCO_3 + HCl \rightarrow NaCl + H_2O + CO_2$
• Overall Reaction for Sodium Carbonate:
  • Equation: $Na_2CO_3 + 2HCl \rightarrow 2NaCl + H_2O + CO_2$
• Indicator Usage:
  • Stage 1 Indicator: phenolpthalin (or phenolpthalein) is used to detect the completion of the first stage of the carbonate neutralization.
  • Stage 2 Indicator: methyl orange is used to detect the completion of the second stage, where all carbonate and bicarbonate are fully neutralized.

EXPERIMENTAL PROCEDURE

Standardization of Hydrochloric Acid ($HCl$)

• Preparation of Standard Solution: Approximately $0.53\,g$ of sodium carbonate ($Na_2CO_3$) was weighed into a volumetric measuring flask. It was dissolved in water to make a total of $100\,cm^3$ solution.
• Titration Steps:
  • A $10\,cm^3$ aliquot of the sodium carbonate solution was pipetted into a conical flask.
  • Two drops of methyl orange indicator were added, which imparted a golden yellow colour to the solution.
  • The solution was titrated with hydrochloric acid ($HCl$) from a burette.
  • End Point: The titration continued until the solution changed from golden yellow to a pale red orange.
• Consistency: The titration was repeated until three concordant readings were obtained to calculate the strength of the $HCl$.

Estimation of Sodium Carbonate and Bicarbonate Mixture

• Preparation: The supplied mixture solution of sodium carbonate and sodium bicarbonate was made up to volume in a measuring flask.
• First Titration Stage (Carbonate to Bicarbonate):
  • $10\,cm^3$ of the mixture was pipetted into a conical flask.
  • One or two drops of phenolpthalein indicator were added, resulting in a pink colour.
  • The mixture was titrated with standard hydrochloric acid until the pink colour was just discharged (disappeared).
  • The burette reading was recorded ($V_1$).
• Second Titration Stage (Total Neutralization):
  • One or two drops of methyl orange were added to the same solution (which remained from the first stage).
  • The titration was continued with the standard hydrochloric acid until the golden yellow colour changed to pale red orange.
  • The final burette reading was recorded ($V_2$).
  • The process was repeated to obtain three concordant readings.

TABULATION AND DATA RECORDING

Tabulation 1: Standardisation of $HCl$ with $Na_2CO_3$

• Aliquot Volume of $Na_2CO_3$: $10\,cm^3$

Tabulation 2: Titration of Mixture

• Volume of Mixture: $10.0\,cm^3$
• $V_1$: Volume of $HCl$ for phenolpthalein end point (representing $1/2 Na_2CO_3$).
• $V_2$: Volume of $HCl$ for methyl orange end point (representing $1/2 Na_2CO_3 + NaHCO_3$).

• Concordant Values:
  • $V_1 (a) = 4.1\,cm^3$
  • $V_2 (b) = 8.2\,cm^3$

CALCULATIONS

Calculation 1: Standardization of $HCl$

• Given/Measured Data:
  • Strength of $Na_2CO_3 = 1.01 × \frac{N}{10}$
  • Volume of $Na_2CO_3 (V_2) = 10\,cm^3$
  • Volume of $HCl (V_1) = 11.2\,cm^3$
• Normality Equation:
  • $N_1V_1 = N_2V_2$
  • $N_{HCl} × 11.2 = 1.01 × \frac{N}{10} × 10$
  • $N_{HCl} = \frac{10.1}{11.2} × \frac{N}{10}$
  • $N_{HCl} = 0.9(2) × \frac{N}{10}$
  • (Used in subsequent calculations as $0.901 × \frac{N}{10}$)

Calculation 2: Estimation of $Na_2CO_3$

• Step 1: Determine equivalents for first stage
  • Number of gram equivalents of $HCl = \text{volume of } HCl × \text{normality} × 10^{-3}$
  • $a = 4.1 × \frac{0.901}{10} × 10^{-3} = 3.694 × 10^{-4}$
• Step 2: Relate to $Na_2CO_3$
  • Number of equivalents of $1/2 Na_2CO_3 = a = 3.694 × 10^{-4}$
  • Total equivalents of $Na_2CO_3 = 2a = 7.388 × 10^{-4}$
• Step 3: Calculate Mass (Equivalent mass of $Na_2CO_3 = \frac{106}{2} = 53$)
  • Weight of $Na_2CO_3 \text{ in } 10\,cm^3 \text{ solution} = 53 × 7.388 × 10^{-4} = 391.5 × 10^{-4}\,g$
  • Weight of $Na_2CO_3 \text{ in } 100\,cm^3 \text{ dilute solution} = 10 × 53 × 7.388 × 10^{-4} = 0.3911\,g$

Calculation 3: Estimation of $NaHCO_3$

• Step 1: Determine equivalents for total neutralization
  • Number of gram equivalents of $HCl$ in stage 2 ($b$) $= 8.2 × \frac{0.901}{10} × 10^{-3} = 7.388 × 10^{-4}$
• Step 2: Relate to mixtures components
  • Number of gram equivalents of $1/2 Na_2CO_3 + \text{whole of } NaHCO_3 = b = 7.388 × 10^{-4}$
  • Gram equivalents of $NaHCO_3 = b - a = (7.388 - 3.694) × 10^{-4} = 3.694 × 10^{-4}$
• Step 3: Calculate Mass (Equivalent mass of $NaHCO_3 = 84$)
  • Weight of $NaHCO_3 \text{ in } 10\,cm^3 \text{ solution} = 3.694 × 10^{-4} × 84 = 310.29 × 10^{-4}\,g$
  • Weight of $NaHCO_3 \text{ in } 100\,cm^3 \text{ dilute solution} = 10 × (b-a) × 84 = 0.3102\,g$

CONCLUSION AND STUDENT DETAILS

• Final Results:
  • Weight of sodium carbonate ($Na_2CO_3$) in mixture: $0.3911\,g$
  • Weight of sodium bicarbonate ($NaHCO_3$) in mixture: $0.3102\,g$
• Student Name: Shalom kumar Naik
• Department: Zoology
• Year/Semester: 1st year 2nd Sem
• Submission Date: 29.09.26