General Science — Chemistry — Practice

Question 1

The chemical formula of common salt is:
(a) NaOH (b) NaCl (c) Na₂CO₃ (d) NaHCO₃

Accepted Answer

(b) NaCl.

Common salt is sodium chloride.

Question 2

Baking soda is chemically known as:
(a) Sodium carbonate (b) Sodium bicarbonate (c) Sodium chloride (d) Sodium hydroxide

Accepted Answer

(b) Sodium bicarbonate.

Baking soda is NaHCO₃; washing soda is the carbonate.

Question 3

The pH of a neutral solution such as pure water is:
(a) 0 (b) 5 (c) 7 (d) 14

Accepted Answer

(c) 7.

pH 7 is neutral; below 7 is acidic, above 7 is basic.

Question 4

Brass is an alloy of:
(a) Copper and tin (b) Copper and zinc (c) Iron and carbon (d) Copper and nickel

Accepted Answer

(b) Copper and zinc.

Bronze is copper + tin; brass is copper + zinc.

Question 5

The most abundant gas in the Earth's atmosphere is:
(a) Oxygen (b) Carbon dioxide (c) Nitrogen (d) Hydrogen

Accepted Answer

(c) Nitrogen.

Nitrogen makes up about 78% of the atmosphere; oxygen about 21%.

Question 6

Diamond and graphite are allotropes of:
(a) Silicon (b) Carbon (c) Sulphur (d) Phosphorus

Accepted Answer

(b) Carbon.

Same element, different structures — diamond is hardest, graphite conducts electricity.

Question 7

The gas commonly used in fire extinguishers is:
(a) Oxygen (b) Hydrogen (c) Nitrogen (d) Carbon dioxide

Accepted Answer

(d) Carbon dioxide.

CO₂ is heavier than air and doesn't support combustion, smothering the fire.

Question 8

The number of protons in the nucleus of an atom is called its:
(a) Mass number (b) Atomic number (c) Valency (d) Atomic mass

Accepted Answer

(b) Atomic number.

The atomic number equals the proton count and identifies the element.

Question 9

Aqua regia, which can dissolve gold, is a mixture of:
(a) HCl and H₂SO₄ (b) HNO₃ and H₂SO₄ (c) HCl and HNO₃ (d) HCl and H₂O

Accepted Answer

(c) HCl and HNO₃.

Aqua regia is concentrated hydrochloric and nitric acids in a 3:1 ratio.

Practice — General Science — Chemistry