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Question
A student prepares solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Solution
Phenolphthalein and methyl orange are also acid-base indicators. They can be used in place of litmus.
Procedure : Transfer a portion of the colourless solutions to two glass tubes. Add one or two drops of phenolphthalein indicator to these. An acid solution will remain colourless while the solution of base will become pink. Now, repeat the experiment with methyl orange indicator. In acid solution, the indicator will become reddish while in base, it will be yellowish.
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