Question

Find the odd one out in each of the following groups, giving reasons for your choice:
(a) litmus, phenolphthalein, turmeric, iodine
(b) citric acid, nitric acid, lactic acid, formic acid
(c) HNO₃, H₂SO₃, H₂SO₄, H₂CO₃
(d) CO₂, SO₂, Na₂O, SO₃
(e) carbonic acid, sulphuric acid, acetic acid, hydrochloric acid
(f) NaOH, Na₂CO₃, Na₂SO₄, NaCl

Answer 1

(a) Iodine: Litmus, phenolphthalein and turmeric are acid base indicators but iodine is not.

(b) Nitric acid: It is a strong acid, while citric acid, lactic acid and formic acid are weak acids.

(c) HNO₃: It is monobasic acid, while H₂SO₃, H₂SO₄ and H₂CO₃ are dibasic.

(d) Na₂O: It is a metal oxide that is basic in nature, while CO₂, SO₂ and SO₃ are non-metal oxides that are acidic in nature.

(e) Sulphuric acid. Because it is a strong acid that furnishes two H⁺ ions but all other acids furnish single H⁺ ions. Carbonic acid, although, contains two hydrogen ions, but because of its weak nature, it furnishes only one of its hydrogen ion under normal conditions.

(f) NaOH: It is a base, while Na₂CO₃, Na₂SO₄ and NaCl are salts.