Question

which substance changes colours of red litmus into blue​

Answer 1

Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F).

Answer 2

Base changes colours of red litmus into blue.

• The pH range of acids lies below 7 and the pH range of bases lies above 7 in pH paper.
• Acid has a sour taste and the base has a bitter taste.
• Acids turn blue litmus paper to blue and base turns blue litmus paper red.
• Some bases like NaOH, KOH, BuLi etc can easily change the colour of red litmus paper to blue.