The aim on my investigation is to find the percentage of citric acid present in lemon squash by using a method of neutralisation, by a method of titration and volumetric analysis.

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Aim:

The aim on my investigation is to find the percentage of citric acid present in lemon squash by using a method of neutralisation, by a method of titration and volumetric analysis. I will be using sodium hydroxide as an alkali, which will be neutralising the citric acid.

Background Knowledge:

Titration

Titration is a technique for investigating the volume of solutions that react together. One solution is placed in a burette and slowly added to a fixed volume of another solution, usually measured with a pipette, until the end point of the reaction is shown using an indicator.

Salts can be made by this method by repeating the titration between an acid and alkali using previously measured quantities without using the indicator.

Citric acid

Citric acid is the acid present in citrus fruits such as oranges and lemons. It is commonly used to add a 'tang' to fruit drinks and lemonades. Mixed with sodium hydrogencarbonate (commonly knows as bicarbonate of soda) and sugar, it becomes sherbet. Its chemical formula is H3 (C6H5O7). In this investigation I will be working out the percentage of this acid in lemon squash using titration

Hydrochloric acid

Hydrochloric acid is a mineral acid. The concentrated acid is a 35% by weight solution hydrogen chloride in water. It is a typical strong acid. It reacts with metals, alkalis and bases, carbonates and indicators in the same way that all strong acid do.

Manufacture of hydrochloric acid

Hydrogen chloride is made industrially by burning hydrogen in chlorine. It is also a valuable by- product of many processes in which chlorine is reacted with organic compounds.

Uses of hydrochloric acid

In the laboratory, concentrated hydrochloric acid will produce chlorine if added to potassium permanganate crystals.

Hydrochloric acid + oxygen atoms from chlorine + water

Potassium

Permanganate

2HCl (aq) + (O) Cl2 (g) + H2O (l)

One of its common industrial uses is to 'pickle' steel. Pickling is the process of dissolving rust from steel articles. The bodies of cars, cookers, and refrigerators are all pickled before painting.

Fe2O3 (s) + 6HCl (aq) 2FeCl3 (aq) + 3H2O

Sodium hydroxide, NaOH

Sodium hydroxide is a white solid which is very soluble in water. In the solid state it is deliquescent- becomes very wet if it is left in the air. It is a typical strong alkali and is used in the manufacture of soaps and aluminium.

Uses of sodium hydroxide

Chemicals -29%

Fibres -16%

Alumina -1%
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Detergents -4%

Paper -5%

Neutralisation -5%

Other uses -40%

Sodium hydroxide is also called caustic soda because of its extremely corrosive nature

Phenolphthalein

Phenolphthalein is an indicator. It is colourless in acidic and neutral solutions and reddish pink in alkaline solutions. It is a common indicator in acid- alkali titration. As the difference can be easily spotted when the solutions is alkaline of acidic I will be using this an indicator in this investigation.

Acids and bases

Acids and Bases are two classes of chemical compounds that display generally opposite ...

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