Sodium carbonate (Na2CO3)

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Analysis of Soda Ash and Volumetric Analysis of a Carbonate-Bicarbonate Mixture Buti, Mary Daphne A.
Department of Chemical Engineering, Faculty of Engineering
University of Santo Tomas
España, Manila

Abstract
Sodium carbonate (Na2CO3), commonly known by trade name soda ash, is a white, anhydrous, powdered or granular material that is an essential raw material used in the manufacturing of glass, detergents, chemicals, and other industrial products. In this experiment, the percent alkalinity of the unknown soda ash sample was determined by titrating it with standard HCl solution. After three trials, the researchers obtained an average percent alkalinity of 33.20% that resulted to a percent error of 12.63%. The percentage of carbonate and bicarbonate of the same unknown soda ash sample was also determined in the experiment, following the same procedures and using the same titrant that is the standard HCl solution; however, this time, the researchers made use of a pH meter. Subsequently, they acquired 22.44% of carbonate and 26.07% of bicarbonate. Introduction

Sodium carbonate (Na2CO3), commonly known by trade name soda ash, is a white, anhydrous, powdered or granular material that is an essential raw material used in the manufacturing of glass, detergents, chemicals, and other industrial products [1]. It has a molecular weight of 105.989 g/mol, melting point of 851̊ C (1564̊ F) and a specific gravity of 2.533 [2]. In the year 1998, soda ash was listed as the 11th largest inorganic chemical of all the organic and inorganic chemicals in terms of production, leaving out petrochemical feedstock [3]. In fact, sodium carbonate has already been in production for more than 5,000 years now. It was used by Ancient Egyptians in making glass ornaments and vessels. The product was recovered from dry lake-bed deposits or by burning seaweed and other marine plants. Even the Romans used soda ash for baking bread, making glass and for medicinal purposes. The extraction of sodium carbonate from the ashes of various plants continued until the middle of 19th century and was now popularly known as “soda ash” [1].

There are two ways of processing sodium carbonate. The most common source is trona, a mineral that occurs in natural deposits in evaporated lake beds throughout the world [4]. It is said that the Green Basin of Wyoming is the world’s largest area for naturally-occurring trona [1]. The other source is through Solvay process which is conducted in a lab. Its product is a synthetic sodium carbonate that though possessing the same properties as that found in nature, it’s more expensive and is harmful to the environment [4].

In this experiment, the percent alkalinity as well as percentage of carbonate and bicarbonate of an unknown soda ash sample will be determined. Alkalinity is a measure of the capacity of water or any solution to neutralize or “buffer” acids. This measure of acid-neutralizing capacity is important in figuring out how “buffered” the water is against sudden changes in pH [5]. First, Hydrochloric acid (HCl) will be standardized and will be used as the titrant. An amount of the unknown soda ash sample will be diluted with distilled water and will be used as the analyte. Two titrations will be conducted. The first one is for the analysis of soda ash while the other one is for the analysis of carbonate and bicarbonate in a mixture wherein the researchers will make use of a pH meter. Phenolphthalein and methyl orange are the indicators that will be used.

Titration is a volumetric technique where the titrant is added into the analyte until the equivalence point is reached. Equivalence point is the point at which an exactly right amount of titrant has been added in order to stoichiometrically react with the analyte. The equivalence point may be signaled by the change in color of the analyte. The color may vary depending on the indicator used. Also, the equivalence point may be obtained using the titration...
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