MCQs on Chemistry

[Set - 1]

1. Which element is known as the "king of chemicals"?

A) Hydrogen
B) Carbon
C) Sulfur
D) Oxygen

Correct Answer: C) Sulfur
Explanation: Sulfur is often referred to as the “king of chemicals” because of its wide range of applications in industry, including in the production of sulfuric acid, which is a key chemical used in many industrial processes.

2. What is the most abundant element in the Earth's crust?

A) Oxygen
B) Silicon
C) Aluminum
D) Iron

Correct Answer: A) Oxygen
Explanation: Oxygen makes up about 46.6% of the Earth’s crust by weight, making it the most abundant element. It is followed by silicon at about 27.7%.

3. Which gas is commonly known as "laughing gas"?

A) Carbon dioxide
B) Methane
C) Nitrogen
D) Nitrous oxide

Correct Answer: D) Nitrous oxide
Explanation: Nitrous oxide (N₂O) is known as “laughing gas” because it can induce a euphoric effect when inhaled, often leading to laughter.

4. What is the chemical formula for table salt?

A) NaCl
B) KCl
C) NaHCO₃
D) CaCO₃

Correct Answer: A) NaCl
Explanation: Table salt is chemically known as sodium chloride, with the formula NaCl.

5. Which element has the highest melting point?

A) Tungsten
B) Iron
C) Carbon
D) Platinum

Correct Answer: A) Tungsten
Explanation: Tungsten has the highest melting point of all elements, at 3422°C (6192°F), making it extremely useful in high-temperature applications.

6. What is the pH value of pure water?

A) 0
B) 7
C) 14
D) 10

Correct Answer: B) 7
Explanation: Pure water is neutral, with a pH value of 7, indicating an equal concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻).

7. Which acid is commonly used in car batteries?

A) Hydrochloric acid
B) Nitric acid
C) Sulfuric acid
D) Acetic acid

Correct Answer: C) Sulfuric acid
Explanation: Sulfuric acid (H₂SO₄) is used in lead-acid batteries found in cars due to its strong acidic nature and ability to act as an electrolyte.

8. What is the lightest metal?

A) Lithium
B) Aluminum
C) Magnesium
D) Sodium

Correct Answer: A) Lithium
Explanation: Lithium is the lightest metal, with a density of about 0.534 g/cm³, and is used in lightweight battery technologies.

9. Which element is used in the filaments of incandescent light bulbs?

A) Copper
B) Aluminum
C) Tungsten
D) Nickel

Correct Answer: C) Tungsten
Explanation: Tungsten is used in light bulb filaments because of its high melting point and durability at high temperatures.

10. What is the common name for the compound H₂O₂?

A) Water
B) Hydrogen peroxide
C) Sulfuric acid
D) Acetone

Correct Answer: B) Hydrogen peroxide
Explanation: H₂O₂ is known as hydrogen peroxide, a chemical compound often used as a disinfectant and bleaching agent.

11. Which gas is known as the "silent killer"?

A) Carbon monoxide
B) Methane
C) Nitrogen
D) Oxygen

Correct Answer: A) Carbon monoxide
Explanation: Carbon monoxide (CO) is called the “silent killer” because it is a colorless, odorless gas that can cause poisoning and death without warning.

12. What is the most common element in the human body by weight?

A) Oxygen
B) Carbon
C) Hydrogen
D) Nitrogen

Correct Answer: A) Oxygen
Explanation: Oxygen makes up about 65% of the human body by weight, mainly found in water molecules.

13. Which element is known as "quicksilver"?

A) Silver
B) Mercury
C) Lead
D) Platinum

Correct Answer: B) Mercury
Explanation: Mercury is commonly referred to as quicksilver due to its liquid state at room temperature and its silvery appearance.

14. What is the chemical name for baking soda?

A) Sodium carbonate
B) Sodium bicarbonate
C) Sodium chloride
D) Sodium hydroxide

Correct Answer: B) Sodium bicarbonate
Explanation: Baking soda is chemically known as sodium bicarbonate (NaHCO₃), used in baking and as an antacid.

15. Which element is used as a moderator in nuclear reactors?

A) Uranium
B) Boron
C) Graphite
D) Plutonium

Correct Answer: C) Graphite
Explanation: Graphite is used as a moderator in nuclear reactors to slow down neutrons, allowing the nuclear reaction to be controlled more effectively.

16. What is the chemical formula for ammonia?

A) NH₃
B) NO₃
C) N₂O
D) NH₄

Correct Answer: A) NH₃
Explanation: Ammonia is a compound with the chemical formula NH₃, consisting of one nitrogen and three hydrogen atoms.

17. Which gas is commonly known as "marsh gas"?

A) Methane
B) Ethane
C) Propane
D) Butane

Correct Answer: A) Methane
Explanation: Methane (CH₄) is known as marsh gas because it is produced by the anaerobic decomposition of organic matter in wetlands.

18. What is the most electronegative element?

A) Fluorine
B) Oxygen
C) Chlorine
D) Nitrogen

Correct Answer: A) Fluorine
Explanation: Fluorine is the most electronegative element, with an electronegativity of 3.98 on the Pauling scale, making it highly reactive.

19. Which element is commonly used in the manufacture of batteries?

A) Lead
B) Lithium
C) Zinc
D) Copper

Correct Answer: B) Lithium
Explanation: Lithium is commonly used in rechargeable batteries, including those in mobile phones and electric vehicles, due to its high electrochemical potential.

20. What is the primary component of natural gas?

A) Propane
B) Butane
C) Ethane
D) Methane

Correct Answer: D) Methane
Explanation: Natural gas primarily consists of methane (CH₄), which is used as a fuel for heating, cooking, and electricity generation.

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