Question

Separate the following into substances having pH values above and below 7. How do these influence litmus paper?
(i) Lemon juice
(ii) Solution of washing soda
(iii) Toothpaste
(iv) Vinegar
(v) Stomach juices

Answer 1

On the pH scale, bases have values greater than 7, whereas acids have values less than 7. A basic solution turns red litmus blue. An acidic solution turns blue litmus red. With this information, let us separate the substances given below into those with pH values above and below 7.

Substances	Acid/base	pH value	Litmus test result
1. Lemon juice	Acid	Less than 7	Turns blue litmus red
2. Solution of washing soda	Base	Greater than 7	Turns red litmus blue
3. Toothpaste	Base	Greater than 7	Turns red litmus blue
4. Vinegar	Acid	Less than 7	Turns blue litmus red
5. Stomach juices	Acid	Less than 7	Turn blue litmus red