Standardization of sulphuric acid.
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Title: Standardization of sulphuric acid Theory: To define the unknown concentration of the sulphuric acid, sodium carbonate solution is used as a standard basic solution to undergo titration. A titration can find out the volume of the sodium carbonate solution which is used to neutralize a specific volume of sulphuric acid in the conical flask or vice versa. The result will be the same as we are objective to define the number of moles of reactants. The number of moles of sulphuric acid can be calculated base on the mole ratio 1:1 for sodium carbonate solution to sulphuric acid in the neutralization. We put sodium carbonate solution in burette and acid in conical flask because less acid should be used for the sake of safety. This time, sodium carbonate is used as a primary standard. A primary standard is a substance which can be used for the direct preparation of a standard solution. This is due to several advantages that sodium carbonate persists: First, it is obtained in high degree of purity. Then, it is stable and unaffected by the atmosphere which implies that the purity will not be affected. Besides, it is available in reasonable price and is not hygroscopic. Finally, its reasonably high relative formula mass reduces the weighing error.
5.For strong acid and carbonate , methyl orange is a ideal indicator. As acid reacts with sodium carbonate to form acidic gas carbon dioxide, the resulting solution is slight acidic due to the dissolved acidic gas. Thus, the equivalent point reached in an acidic solution. Hence, Methyl orange, which has a low pKin value is used in this time. Although the end point this time can not be determined by using indicator for all acid-alkali titration, we can determine it by alternative means like using pH meter, and by conductivity measurements. Procedure: 1 Preparation, washing and cleaning of apparatus. a . The pipette was washed by tap water first , followed by distilled water and finally With the sulphuric acid. b. The conical flask was washed by tap water first, and then distilled water . c. The burette was washed with tap water, distilled water and finally rinsed with sodium carbonate solution. d. Beaker, filter funnel, volumetric flask should be rinsed with distilled water . * Beaker used to contain sulphuric acid, filter funnel for translating carbonate solution into burette should be dried completely lest the dilution of solution. 2 To make a standard solution of sodium carbonate a. Weigh about 2.65g of sodium carbonate .A weighing bottle should be used to contain the weighed sodium carbonate.
The solution should be orange in color now. h. The solution is then added drop by drop now. After adding each drop of solution, the level should be recorded until the color turns to yellow. i. The resultant volume should be recorded just before the color change of yellow. j. The steps f to I should be repeated for at least 3 times to obtain a consistent result. Discussion: The final result is deviated from the exact answer. This is due to several errors. For instance, the reading is the end point reading, it is not the equivalent point. In addition, the end point may be difficult to observe as changing from red to orange is not particularly clear. To tackle these problems, a pH meter can be used to find out the point instead of using indicators. Besides, there may be some impurities in the sodium carbonate. Then, the incomplete washing and cleaning of apparatus may cause errors. For example, the beaker, pipette has not dried and contains some water inside. This will lead to the dilution of the acid. So, we should make sure that these apparatus are completely dried. The volumetric flask may not wash and clean thoroughly with a brush or the brush is dirty itself, this will cause some water in flask stick on the glass. Consequently, the flask will not contain 250ml solution exactly. We should use some dishwashing liquid and a clean brush to clean the volumetric flask.
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