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ACIDS,BASES AND INDICATORS
FLOWER EXTRACT AS ACID/BASE INDICATOR
One way of classifying substances in Chemistry is by finding out whether they are basic or acidic using flower extract .Acids are found in many naturally occuring materials which are used in everyday life. some occur in the foods we eat such as lemons and other citrus fruits, vinegar and some soft drinks. In the laboratory there are various acids which are used for example Sulphuric and Hydrochloric acid. These are reffered to as mineral acids.
Bases are substances that react acids to give a salt and water.
By the end of the topic you should be able to:
1. Prepare flower extracts as acid- base indicators
2.Use the flower extract as acid- base indicators
3.Use common commercial acid- base indicators to identify acids and bases
4.State simple properties of acid and bases
5.List uses of acids and bases
PREPARATION OF ACID/BASE INDICATOR FROM FLOWER EXTRACTS
Crush some flower petals in a mortal using a pestle.Add a little of propanone or ethanol.Grind the petals until enough extract of the flower is collected.Filter into a clean test tube.
The flower extract can be used to test if a substance is basic or acidic by adding the extract to different solutions.
Commercial indicators can be used to test whether a substance is acidic or basic. The following experiment shows what is observed when commercial indicators are added to different acids and bases. Dilute Hydrochloric acid is placed in test-tube 1, 2 and 3 while ammonia solution is placed in test-tube 4,5 and 6.Two drops of methyl orange is added to test-tube 1 and 4. Two drops of phenolphthalein indicator are added to test-tube 2 and 5. Blue and red litmus papers are placed intotest-tube3 and 6
UNIVERSAL INDICATOR AND pH SCALE
Different indicators form different colours in various solutions. The indicators provide no information about the strength of an acid or base. The universal indicator exhibit a range of colours in acids and bases depending on the acidic and basic strength of the solution.These ranges of colours are compared to a continuous acid/base scale called the pH scale. The pH scale has values ranging from 1 - 14.
pH 1-3 are classified as strongly acidic
pH 4-6 are weakly acidic
pH 7 is neutral
pH 8-11 are weakly basic,
pH 12-14 are strongly basic.
The colours of a universal indicator correspond to different pH values, ranging from 1-14.
A pH chart can be used to show both the colour and pH of a substance.
The pH chart can be used to show the strength of different solutions.
Sulphuric acid turns red hence a strong acid.Ethanoic acid turns yellow indicating that it is a weak acid.Water turns to green showing that it is neutral.Ammonia solution turns to blue showing that it is a weak base while Sodium Hydroxide solution turns to a deep blue solution indicating that it is a strong base.
ALKALINITY AND ACIDITY ON THE pH SCALE
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