1. The substance which turns blue litmus red is
(a) neutral
(b) acidic
(c) basic
(d) alkaline
2. The acid present in curd/sour milk is
(a) formic acid
(b) acetic acid
(c) lactic acid
(d) hydrochloric acid
3. H₂SO₄ is
(a) an acid
(b) a salt
(c) a base
(d) an alkali
Answer (2)
The substance which turns blue litmus red is (b) acidic.
Litmus is a type of indicator paper used to test whether a substance is acidic or basic. When blue litmus paper comes in contact with an acidic substance, it turns red. This is because acids increase the concentration of hydrogen ions (H⁺) in solution, which reacts with the dye in the litmus paper to change its color.
The acid present in curd/sour milk is (c) lactic acid.
Curd or sour milk contains lactic acid, which is produced when bacteria ferment lactose, the sugar found in milk. Lactic acid is what gives sour milk its tangy flavor as it decreases the pH level, making the milk sour.
H₂SO₄ is (a) an acid.
H₂SO₄ is the chemical formula for sulfuric acid. It is a strong acid commonly used in industrial processes as well as in car batteries. It dissociates in water to form hydrogen ions, contributing to its acidic properties.
The correct answers are: 1) (b) acidic for turning blue litmus red, 2) (c) lactic acid in curd, and 3) (a) H₂SO₄ is an acid. Each component is essential in identifying properties of acids in different contexts, including their reactions with litmus, their presence in food, and their industrial applications.
;
