Question

Solution A turns universal indicator from blue to purple whereas solution B turns universal indicator from orange to red.
1) Name any two substances that can give solutions like A.
2) Name any two substances that can give solutions like B.
If the answer to 1) is Lemon Juice and Hydrochloric Acid, then how is it possible, because one is a weak acid and the other is a strong acid.

Answer 1

1. The solution which change the universal indicator colour from blue to purple should have the pH range 6-11. That means strong bases like NaOH and KOH shows this. So titration of weak acid (pH range 6-7 ) which shows blue colour with universal indicator with strong bases (pH range > 11 ) which shows purple colour
2. The soultion which change the universal indicator colour from orange to red should have the pH range 3-6. That means strong acid like HCl, sulphuric acid titrated against weak bases NH₄OH