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Determination of the Molar Mass of a Dibasic Acid.

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Elmaz Korimbocus Determination of the Molar Mass of a Dibasic Acid INTRODUCTION A dibasic acid is one in which there are two hydrogen atoms which can be donated as protons (H+):- If a solution of this dibasic acid is titrated with a standard base, the concentration of the acid solution can be determined and ultimately so can the molar mass. PROCEDURE APPARATUS * Weighing scales * Weighing bottle * Solid dibasic acid * Beaker * Distilled water * 250cm3 volumetric flask * Stopper * Pipette * 250cm3 conical flasks * Phenolphthalein indicator * Burette * Sodium hydroxide Using the weighing scales, 1.5 - 1.7g of the solid dibasic acid was weighed out into a weighing bottle, not including the mass of the weighing bottle. The solid dibasic acid was transferred into a beaker, making sure that every last bit of the acid had gone into the beaker. The acid was dissolved in approximately 150cm3 of distilled water. ...read more.


The mean titre was needed, and worked out by:- 22.1 + 24.1 + 24.2 = 70.4 ? ? ? 1st 2nd 3rd titre titre titre 70.4 = 23.47 because there were 3 readings ? 3 CALCULATIONS AND ANALYSIS The following needed to be determined before the molar mass of the dibasic acid could be found:- * The number of mols of sodium hydroxide in the mean titre * The number of mols of dibasic acid in 25cm3 * The number of mols of dibasic acid in 250cm3 and therefore the mass that was weighed out So, the number of mols of sodium hydroxide (NaOH) was found using the equation:- Concentration x Volume 1000 With my figures:- 0.1 x 23.47 1000 = 0.002347 mols of NaOH in the mean titre The ratio of acid and alkali is:- Dibasic acid : Alkali 2H+ : OH- 1 : 2 Therefore, knowing the ratio and the number of mols of the alkali, the number of mols of acid in 25cm3 of solution could be determined:- Acid ...read more.


* In acid solutions the pH is less than 7, the lower the pH the greater the acidity. * In alkaline solutions the pH is greater than 7. * In aqueous solution strong acid are fully dissociated. * For example, sodium hydroxide dissociates: NaOH(aq) � Na+(aq) + OH-(aq) * In aqueous solution weak acids are partially dissociated. * For example, the weak acid ethanoic acid dissociates: CH CO H (aq) CH CO -(aq) + H+ (aq) As I was using a weak acid/strong base titration (ethanoic acid and sodium hydroxide), methyl orange solution would not have been adequate, as it does not change vertically on the graph from the previous page. Phenolphthalein will change sharply at exactly 25.0cm3 (as shown on the graph), the equivalence point, therefore a perfect choice for my experiment, as those were the volumes I was dealing with. My titration went to plan and that can be seen by the fact that the molar mass I worked out from my results is realistic. HEALTH AND SAFETY Using acid, there are always precautions to be considered, such as wearing eye protection, lab coats and gloves to prevent burning. ...read more.

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