![SHREE MALLIKARJUN COLLEGE
CLASS:FYBSC
SAFETY: Refer to MSDS of hydrochloric acid, sodium bicarbonate, sodium carbonate,
phenolphthalein and methyl orange
-Dr. Mithil S.Fal Desai
Aim: Estimation of sodium carbonate and sodium hydrogen carbonate present in a mixture.
Chemicals: Hydrochloric acid, sodium carbonate, sodium bicarbonate, methyl orange and
phenolphthalein.
Apparatus: Standard volumetric flask, pipette, burette, conical flask, beakers, funnel and glass rod.
Theory: The aqueous solution of sodium carbonate (Na2CO3) and sodium hydrogen carbonate (NaHCO3)
is basic. Volumetric analysis of any base can be done by titrating a standardized acid solution using a pH-
sensitive indicator. The product of acid and base titration is salt which usually has neutral pH. In aqueous
solution Na2CO3 and NaHCO3) exist as a carbonate (CO3
2-
(aq)) and bicarbonate (HCO3
-
(aq)) molecular ion.
CO3
2-
(aq) + H+
(aq) HCO3
-
(aq) (Reaction-1) Methyl red and phenolphthalein
HCO3
-
(aq) + H+
(aq) H2CO3 (aq) H2O (l) + CO2 (g) (Reaction-2) Methyl red
The completion of Reaction-2 can be analyzed using phenolphthalein or methyl orange indicator.
However complete neutralization of bicarbonate (Reaction-2) cannot be studied using phenolphthalein
indicator. The mixture of carbonates and bicarbonate as the solution will be pink in colour once the
available carbonate forms bicarbonate ( around pH )8. Thus, Reaction-2 could be effectively studied using
the methyl red indicator only.
The use of pH-sensitive indicators such as phenolphthalein [colourless pH(8.0-9.6) pink] and methyl
orange [red pH(3.1- 4.4) yellow] can differentiate these chemical species by neutralization with dilute
mineral acids.
Procedure: I) Standardisation of 0.1N (appx.) HCl (Reference-2)
II) Estimation of bicarbonate and carbonate in the mixture.
1) Pipette out 10 mL of the mixture in a conical flask add 2 drops of methyl orange indicator.
2) Titrate against standardized 0.1N HCl (appx.) solution and repeat the titration for constant
readings.
3) Similarly, titrate the 10 mL of mixture against standardized 0.1N HCl using phenolphthalein
indicator
4) Repeat the titration until a constant reading is observed.
Further reading (available in the library)
1) Experiments in Applied Chemistry, S. Rattan, S. K Kataria and Sons.
2) Vogel’s textbook of quantitative chemical analysis, J. Mendham, R. C. Denney, J. D. Barns, M.
Thomas, B. Sivasankar, Pearson India Education, 6th
Edition.
Questions
1) Which amongst the following is/are the primary standards? Why?](https://image.slidesharecdn.com/estimationofsodiumbicarbonateandcarbonateinmixture-201021051010/85/Estimation-of-sodium-bicarbonate-and-carbonate-in-mixture-1-320.jpg)
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Estimation of sodium bicarbonate and carbonate in mixture
- 1. SHREE MALLIKARJUN COLLEGE CLASS:FYBSC SAFETY: Refer to MSDS of hydrochloric acid, sodium bicarbonate, sodium carbonate, phenolphthalein and methyl orange -Dr. Mithil S.Fal Desai Aim: Estimation of sodium carbonate and sodium hydrogen carbonate present in a mixture. Chemicals: Hydrochloric acid, sodium carbonate, sodium bicarbonate, methyl orange and phenolphthalein. Apparatus: Standard volumetric flask, pipette, burette, conical flask, beakers, funnel and glass rod. Theory: The aqueous solution of sodium carbonate (Na2CO3) and sodium hydrogen carbonate (NaHCO3) is basic. Volumetric analysis of any base can be done by titrating a standardized acid solution using a pH- sensitive indicator. The product of acid and base titration is salt which usually has neutral pH. In aqueous solution Na2CO3 and NaHCO3) exist as a carbonate (CO3 2- (aq)) and bicarbonate (HCO3 - (aq)) molecular ion. CO3 2- (aq) + H+ (aq) HCO3 - (aq) (Reaction-1) Methyl red and phenolphthalein HCO3 - (aq) + H+ (aq) H2CO3 (aq) H2O (l) + CO2 (g) (Reaction-2) Methyl red The completion of Reaction-2 can be analyzed using phenolphthalein or methyl orange indicator. However complete neutralization of bicarbonate (Reaction-2) cannot be studied using phenolphthalein indicator. The mixture of carbonates and bicarbonate as the solution will be pink in colour once the available carbonate forms bicarbonate ( around pH )8. Thus, Reaction-2 could be effectively studied using the methyl red indicator only. The use of pH-sensitive indicators such as phenolphthalein [colourless pH(8.0-9.6) pink] and methyl orange [red pH(3.1- 4.4) yellow] can differentiate these chemical species by neutralization with dilute mineral acids. Procedure: I) Standardisation of 0.1N (appx.) HCl (Reference-2) II) Estimation of bicarbonate and carbonate in the mixture. 1) Pipette out 10 mL of the mixture in a conical flask add 2 drops of methyl orange indicator. 2) Titrate against standardized 0.1N HCl (appx.) solution and repeat the titration for constant readings. 3) Similarly, titrate the 10 mL of mixture against standardized 0.1N HCl using phenolphthalein indicator 4) Repeat the titration until a constant reading is observed. Further reading (available in the library) 1) Experiments in Applied Chemistry, S. Rattan, S. K Kataria and Sons. 2) Vogel’s textbook of quantitative chemical analysis, J. Mendham, R. C. Denney, J. D. Barns, M. Thomas, B. Sivasankar, Pearson India Education, 6th Edition. Questions 1) Which amongst the following is/are the primary standards? Why?
- 2. SHREE MALLIKARJUN COLLEGE CLASS:FYBSC SAFETY: Refer to MSDS of hydrochloric acid, sodium bicarbonate, sodium carbonate, phenolphthalein and methyl orange -Dr. Mithil S.Fal Desai HCl, Na2CO3,NaHCO3 2) What is the equivalent weight of Na2CO3 and NaHCO3 according to reaction 1 and 2? 3) Why an indicator is required in the experiment?