Question

When does the colour of blue litmus turn red?

Answer 1

Litmus paper:

• Litmus paper is a paper which shows the colour change in an acidic/basic solution.
• It shows whether the solution is acidic or basic.
• When exposed to an acidic solution, blue litmus turns red, in the basic solution, the red litmus changes to a blue colour.

Blue to red:

• The blue litmus paper turns when the solution is acidic, while the red litmus paper turns blue under basic or alkaline conditions over the $\mathrm{pH}$ range $4.5-8.3\mathrm{at}{25}^{°}\mathrm{C}$.
• Litmus paper in purple colour is neutral.