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Introduction

Experiment 2 Name Teoh Han Xuan ID No 11ADB05289 Partners Name Loo De Jing Date 13 June 2012 Title The use of volumetric flask, burette and pipette in determining the concentration of NaOH solution Objectives 1. To carry out acid base titration 2. To determine the end point with the use of indicators such as phenolphthalein Introduction In a titration, a burette is used to dispense measured increments of one solution into a known volume of another solution. The object of the titration is the detection of the equivalence point. In the reaction of HCl and Naoh, the equivalence point does occur when same mole of HCl has reacted with same mole of NaOH. The titration technique can be applied to many types of reactions, including oxidation-reduction, precipitation, complexation and acid-base neutralization reactions. An indicator is a substance that undergoes a distinct color change occurs is called the end point of titration, the indicator used in a titration must be selected carefully. Material & Apparatus NaOH solution, HCl solution, Phenolphthalein solution, Beaker, Burette, Pipette, Volumetric flask, Erlenmeyer flask, Funnel, Watch Glass Procedures 1. The volumetric flask was cleaned and rinsed with distilled water 2. ...read more.

Middle

The ionic equation is shown below: 1. HIn H+ + In- An indicator is added to the solution being titrated. The indicator is a substance that changes color when the reaction is complete. Phenolphthalein, which is a commonly used acidâbase indicator, is added to the nitric acid solution in the Erlenmeyer flask. Phenolphthalein has two chemical forms. In acidic conditions, it is in the acid form, which is colorless. In basic conditions, an H+ ion is removed from each phenolphthalein molecule, converting it to its base form, which is red. Furthermore, weak acids are titrated in the presence of indicators which change under alkaline conditions while weak bases are titrated by the indicator that under acidic conditions. Moreover, the indicator does not change color from pure acid to pure alkaline at specific hydrogen ion concentration, but rather, color change occurs over a range of hydrogen ion concentrations. Some common acid base indicators can be used. Tried and true indicators are bromphenol blue, bromcresol green, methyl red, bromthymol blue, phenol red, neutral red, phenolphthalein and so forth. Indicators pH Range Acid Base Bromphenol blue 3.0-4.6 Yellow Blue – violet Bromcresol green 4.0-5.6 Yellow Blue Methyl red 4.4-6.2 Red Yellow Bromphenol blue 6.2-7.6 Yellow Blue Phenol red 6.4-8.0 Yellow Red Neutral red 6.8-8.0 ...read more.

Conclusion

The meniscus is the curved upper surface of the liquid in a burette. When viewing the burette with the volumetric scale toward you, follow the lowest point at the surface of the liquid to the wall of the burette. Read the volumetric scale at this point. It is essential that the meniscus be at eye level when determining the volume. Furthermore, always add acid to water, not water to acid, to avoid excess heat formation and spitting of acid. Stir solution while adding acid. Acid strength use the terms "strong" and "weak" to give an indication of the strength of an acid. The terms strong and weak describe the ability of acid solutions to conduct electricity. If the acid conducts electricity strongly, it is a strong acid. If the acid conducts electricity weakly, it is a weak acid or base. Moreover, acid concentration is well defined that how many acid molecules per unit volume in the solution. A weak base is a chemical base that does not ionize fully in an aqueous solution, defining as a chemical base in which protonation is incomplete. Nonetheless, Insoluble Bases are usually the Metal Oxides such as Magnesium Oxide, Copper (II) Oxide, Lead (II) Oxide, Iron (III) Oxide and Iron (II) Oxide. Conclusion: The initial concentration of NaOH is 0.01M. The average volume of NaOH used is 26.79 mL. ...read more.

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