Titration Lab Report(2nd round)

Titration Lab Report(2nd round) - Titration Lab Report...

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Titration Lab Report Wenting Guo 10/14/08 Purpose: A series of titration was conducted to precisely determine the concentration of a strong acid, hydrochloric Acid (HCl.) Titration was used because, by doing titration, the end point where the moles of the acid were equal to the moles of the base is easily to see as the indicator changes its color. The amount (in moles) and volume (in ml) of the acid and therefore the concentration will then be precisely measured. Methods: At the end point of the titration, the moles of monoprotic acid are equal to the moles of base, so titration will be used to determine the molarity of Hydrochloric acid in this experiment. We titrate to determine precisely the molarity of hydrochloric acid solution by measuring how much a weak base (TRIS, tris-(hydroxymenthyl) aminomethane it took to neutralize the solution. To visually see the end point of this titration, an acid-base indicator, Bromocresol Green (BCG), was added to the solution. BCG was used instead of other indicators because it turned green in a neutral solution when it changed from blue in a basic solution to yellow in an acidic solution. The weak base was used as a primary standard since it was a solid which can be obtained in high purity. As moles of acid added from the buret equaled the moles of base at the end point as the solution turned green, the moles of acid were precisely determined. The volume of the added acid was also precisely determined since the buret of a titration apparatus was calibrated to 0.10 ml, and the stopper enabled a drop-by-drop control of a volume of solution when it was close to the equivalence point. As we measured the mass and the volume in titration, the molarity of the HCl solution was then precisely determined. Proper use of equipment leads to a precise result. There are a few instruments used in this experiment that enable a high control during transferring solution, dilution, and especially titration. Key instruments and their functionalities were listed below: Key instruments: By weighing accurately the mass of the base in a weighing boat on a digital balances, the moles of the base in the solution will be calculated according to equation (1) Mol=mass/molar mass. -A digital balances and a weighing boat measure out TRIS solid to four digital places. -A 5ml Pipette was used to transfer the exact volume of a solution. - A 250.00ml volumetric flask was used to dilute the concentrated HCl solution. By stoppering the flask and turning end over end several times, students can mix the acid well so that the acid used for each the titration will be the same. The same molarity of diluted acid for each trial enables the possible precise result.
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-A 250ml Erlenmeyer flask was used to hold the TRIS solution. During titration, we
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This note was uploaded on 05/09/2010 for the course BIO biology taught by Professor Meighan during the Spring '09 term at Berkeley.

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Titration Lab Report(2nd round) - Titration Lab Report...

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