Quantitative Analysis of Soda Ash by Double-Indicator Titration

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EXPERIMENT NO. 7

Quantitative Analysis of Soda Ash by Double-Indicator
Titration
ABSTRACT
This experiment aims to analyze the percent composition of a substance mixture by using double indicator titration. The analyte used is the soda ash which is titrated with an HCl titrant, standardized by 1o Na2CO3. The indicators used are phenolphthalein for basicity and methyl orange for acidity. The two volumes of the titrant are then used to calculate percent composition of soda ash analyte. Statistical parameters such as relative standard deviation and confidence limits are also calculated. At the end of the experiment, the calculate percent /calculated average percent by mass of Na2CO3 is 27.6% with a relative standard deviation of 64.1 ppt and confidence intervals of 43.5% - 11.7% and the average percent by mass of NaHCO3 is 5.23% with a relative standard deviation of 128 ppt and confidence intervals of 11.3% - -0.8%. With these results and the fulfilled objectives, the experiment was a success

Introduction
This experiment focuses in the analysis of soda ash,
a widespread industrially used substance in
petroleum refining, glass making, detergent
manufacture, water treatment etc. It can be a pure
compound of sodium carbonate, sodium
bicarbonate or sodium hydroxide or the mixture of
the three with compatible percent compositions.
These compositions are determined by acid-base
titrations, a volumetric process in determining the
concentration of a substance in a certain solution
which uses a base or acid as the titrant.
The reaction between sodium carbonate and
hydrochloric acid occurs in 2 stages, with the
formation of bicarbonate ion as the intermediate
product.
(1)
(2)
Equation 1 shows the production of the bicarbonate
ion in the first titration and equation 2 shows that
the bicarbonate is consumed in the second titration.

Graph 1. Endpoints of HCl with Na2CO3 and
NaHCO3
Graph 1 shows that sodium carbonate has two
endpoints, the...
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