Chemistry MCQ 2026 – Topic-wise Practice for SSC, Railways, UPSC

What is the chemical formula of water?

H2O

H3O

H2O2

Easy

💡 Explanation

Water (H₂O) consists of two hydrogen atoms and one oxygen atom. H₂O₂ is hydrogen peroxide.

Which planet is known as the "Red Planet"?

Jupiter

Saturn

Mars

Venus

Easy

💡 Explanation

Mars is called the "Red Planet" because of the reddish iron oxide (rust) on its surface, giving it a distinctive red appearance.

The speed of light in vacuum is approximately:

3 × 10⁶ m/s

3 × 10⁸ m/s

3 × 10¹⁰ m/s

3 × 10⁴ m/s

Easy

💡 Explanation

The speed of light in vacuum (c) is approximately 3 × 10⁸ metres per second, or about 300,000 km/s.

The unit of electrical resistance is:

Volt

Ampere

Watt

Ohm

Easy

💡 Explanation

The SI unit of electrical resistance is the Ohm (Ω), named after physicist Georg Simon Ohm who formulated Ohm's Law.

Which gas is most abundant in the Earth's atmosphere?

Oxygen

Carbon Dioxide

Nitrogen

Argon

Easy

💡 Explanation

Nitrogen (N₂) makes up about 78% of the Earth's atmosphere. Oxygen is second at about 21%.

The process by which plants make food using sunlight is called:

Respiration

Photosynthesis

Transpiration

Fermentation

Easy

💡 Explanation

Photosynthesis is the process by which green plants use sunlight, water, and carbon dioxide to produce oxygen and glucose (food).

Which is the hardest natural substance on Earth?

Gold

Iron

Diamond

Quartz

Easy

💡 Explanation

Diamond is the hardest natural substance, rating 10 on the Mohs hardness scale. It is a form of carbon with atoms arranged in a crystal structure.

The human body has how many pairs of chromosomes?

Medium

💡 Explanation

The human body has 23 pairs of chromosomes (46 total in each cell). The 23rd pair determines biological sex (XX for female, XY for male).

Who developed the theory of relativity?

Isaac Newton

Albert Einstein

Niels Bohr

Max Planck

Easy

💡 Explanation

Albert Einstein developed the Special Theory of Relativity (1905) and the General Theory of Relativity (1915), revolutionizing our understanding of space, time, and gravity.

ISRO's Chandrayaan-3 successfully landed on the Moon in:

July 2023

August 2023

September 2023

October 2023

Medium

💡 Explanation

ISRO's Chandrayaan-3 Vikram lander successfully touched down near the Moon's south pole on 23 August 2023, making India the 4th country to achieve a soft lunar landing.

Which scientist is credited with the discovery of the theory of evolution through natural selection?

Charles Darwin

Galileo Galilei

Isaac Newton

Albert Einstein

Medium

💡 Explanation

Charles Darwin is credited with the discovery of the theory of evolution through natural selection, which he published in his book 'On the Origin of Species' in 1859.

Which scientist is credited with the discovery of the X-ray?

Wilhelm Conrad Rontgen

Marie Curie

Pierre Curie

Henri Becquerel

Medium

💡 Explanation

Wilhelm Conrad Rontgen is credited with the discovery of the X-ray in 1895, for which he was awarded the first Nobel Prize in Physics in 1901.

Which scientist is credited with the discovery of the polio vaccine?

Jonas Salk

Albert Sabin

Edward Jenner

Louis Pasteur

Medium

💡 Explanation

Jonas Salk is credited with the discovery of the inactivated polio vaccine, which was first introduced in 1955 and has since been used to nearly eradicate polio worldwide.

Which scientist is credited with the discovery of the structure of DNA?

James Watson and Francis Crick

Rosalind Franklin and Maurice Wilkins

Linus Pauling and Robert Corey

Erwin Chargaff and Marshall Nirenberg

Medium

💡 Explanation

James Watson and Francis Crick are credited with the discovery of the structure of DNA in 1953, using X-ray crystallography data provided by Rosalind Franklin and Maurice Wilkins.