2.28: Describe the Use of Litmus, Phenolphthalein and Methyl Orange to Distinguish Between Acidic and Alkaline Solutions

LITMUS:

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• Litmus indicator solution turns Red in Acidic solutions, Blue in Alkaline solutions, and Purple in Neutral solutions
• Litmus paper is usually more reliable - comes as Red litmus paper or Blue litmus paper

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	RED LITMUS	BLUE LITMUS
ACIDIC SOLUTION	Stays Red	Turns Red
NEUTRAL SOLUTION	Stays Red	Stays Blue
ALKALINE SOLUTION	Turns Blue	Stays Blue

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PHENOLPHTHALEIN & METHYL ORANGE:

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• Phenolphthalein changes colour sharply at approximately pH 8, and is commonly used in titrations
• Methyl Orange is a solution and changes into a range of warm colours

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INDICATOR	ACID	NEUTRAL	ALKALI
PHENOLPHTHALEIN	Colourless	Colourless	Pink
METHYL ORANGE	Red	Yellow	Yellow