Question

During one of her magic tricks when Sarah rubbed the white paper with a handkerchief, blue letters appeared. Which of the following materials might have been used by her in the magic trick?

• A. Methyl orange and hydrochloric acid.
• B. Soap and hibiscus juice.
• C. Sulphuric acid and phenolphthalein.
• D. Vinegar and turmeric.

Answer 1

The correct option is B

Soap and hibiscus juice.

Indicators are substances that help us to distinguish between acids and alkalis through color change.
The following table depicts the colour change observed when these indicators are added in acidic or basic medium:

$$\begin{array}{ccc}\text{Indicator}& \text{Acidic}& \text{Basic}\\ \text{Methyl orange}& \text{Pale pink}& \text{Pale yellow}\\ \text{Phenolphthalein}& \text{Colourless}& \text{Pink}\\ \text{Turmeric}& \text{Yellow}& \text{Red}\\ \text{Hibiscus juice}& \text{Red}& \text{Blue}\end{array}$$
Hibiscus juice is blue in colour which remains the same in basic solution and gives red colour in acidic medium. In a soap (basic) solution, it will give a blue colour. Hence we can conclude that the materials used here for the magic trick are soap and hibiscus juice.