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Acid-Base titration of Sulphuric acid and Sodium Hydroxide
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Introduction
ACID - BASE TITRATION AIM The aim is to perform an experiment involving the titration of an acid and base to find the end-point of the titration in order to determine the molarity of the sulphuric acid. GENERAL BACKGROUND According to Bronsted and Lowry (1923) an acid is defined as a proton (H+) donor, and a base as a proton (H+) acceptor. For example, sulphuric acid, a strong acid, is a good proton donor while sodium hydroxide, a strong alkali (soluble base) contains the hydroxide ion (OH-) which is a strong proton acceptor. The alkali which produces this OH- ion will neutralize acids by the reaction: H+(aq) + OH-(aq) --> H2O(l) This reaction is common to all neutralization reactions between acids and alkalis in aqueous solution. It should be noted that in aqueous solutions the H+ ions exist in their hydrated forms H+(aq). The most accurate method of measurement is to run the acid into the alkali from a burette. This is known as neutralization by titration. Titration is a technique used to find the concentration flask. ...read more.
Middle
CONTROLLED VARIABLES * The volume of sodium hydroxide in the conical flask was kept constant at a volume of 25cm3 * The molarity of sodium hydroxide used was kept constant at a value of 0.1mol/dm3. * The number of drops of phenolphthalein indicator that was added in the conical flask was kept constant at 3-4 drops. APPARATUSES AND CHEMICALS USED * 2 beakers of 250ml each * 1 pipette of 25ml with pump * 1 burette of 50ml * 1 metal retort stand * 1 white tile * 1 conical flask of 250ml * 0.1M of Sodium Hydroxide ( NaOH ) * Unknown molarity of Sulphuric acid ( H2SO4 ) * Phenolphthalein indicator METHOD * First, I rinsed out the burette with a little distilled water followed by a little distilled water followed by a little dilute sulphuric acid. Then I filled the burette with dilute sulphuric acid and recorded the initial burette reading in a suitable results table. * Then I rinsed out the pipette with some 0.1M sodium hydroxide and then carefully transferred 25cm3 of the NaOH solution to a conical flask * Then I added 3-4 drops of phenolphthalein solution to the flask. ...read more.
Conclusion
= 0.1 M x 0.025 dm3 = 0.0025 moles No. of moles of Sulphuric acid = 0.5 x No. of moles of NaOH neutralized = 0.5 x 0.0025 = 0.00125 moles Concentration of Sulphuric acid = No. of moles of H2SO4 Volume of H2SO4 (dm3) = 0.00125 0.0239 = 0.052M CONCLUSION After conducting the above the experiment carefully and systematically I conclude that the concentration of sulphuric acid that was used in the experiment is 0.05mol/dm3. I also conclude that from the chemical equation the molar ratio of sulphuric acid to sodium hydroxide is 1: 2. . EVALUATION The sources of error that was present when doing the experiment was parallax error. The measurement of the liquid was supposed to be read from the lower meniscus. The lab should have burettes with a better stopper so as to allow different amount of volumes to pass through. There should be better pumps for sucking the liquid through the pipette. The method used here in order to perform the titration gave me the concentration of sulphuric acid to be 0.05mol/dm3, hence the method used was effective. ?? ?? ?? ?? Arshad Akber IB1 Page 1 ...read more.
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