Question

A student prepared solution 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 ?

Answer 1

In the absence of litmus, any other indicator like methyl orange, phenolphthalein, etc., can be used. Otherwise a natural indicator like turmeric can also be used.
Some common indicators with characteristic colours are tabulated below
$\begin{array}{ccccc}\text{S.No.}& \text{Indicator}& \text{Colour in acidic}& \text{Colour in neutral}& \text{Colour in basic}\\ & & \text{solution}& \text{solution}& \text{solution}\\ 1.& \text{Litmus}& \text{Red}& \text{Purple}& \text{Blue}\\ 2.& \text{Phenolphthalein}& \text{Colourless}& \text{Colourless}& \text{Pink}\\ 3.& \text{Methyl orange}& \text{Red}& \text{Orange}& \text{Yellow}\\ 4.& \text{Turmeric Juice}& \text{Yellow}& \text{Yellow}& \text{Red}\end{array}$