All Free Everyday Science MCQs with Answers

421. For glavinizing of iron which of the following metals is used ?

• A. Aluminimum
• B. Copper
• C. Zinc
• D. Lead

Explanation: Galvanizing protects iron by coating it with zinc, which acts as a barrier and also corrodes preferentially if the coating is damaged. This sacrificial protection is why zinc is used rather than copper or lead.

422. Which of the following is the lightest substance?

• A. Uranium
• B. Hydrogen
• C. Oxygen
• D. Nitrogen

Explanation: Hydrogen has the lowest atomic and molecular mass of all elements, making it lighter than oxygen, nitrogen and uranium. In ordinary conditions, hydrogen exists as a very light gas.

423. Permanent hardness of water may be removed by the addition of___________?

• A. Sodium Carbonate
• B. Alum
• C. Potassium Permanganate
• D. Lime

Explanation: Sodium carbonate reacts with dissolved calcium and magnesium salts and precipitates them, removing permanent hardness. Alum is mainly used as a coagulant, while lime is chiefly used for temporary hardness.

424. Crude Oil is heated in the furnace up to _________?

• A. 300°C
• B. 350°C
• C. 400°C
• D. 450°C

Explanation: In fractional distillation, crude oil is heated in a furnace to roughly 350 to 400°C before entering the fractionating column. Among the given choices, 400°C is the usual approximate value.

425. Which gas is used for artificial ripening of green fruit ?

• A. Carbon dioxide
• B. Acetylene
• C. Ethane
• D. Ethylene

Explanation: Ethylene is a natural plant hormone that triggers fruit ripening and is therefore used commercially to ripen green fruit. Acetylene can have similar effects in some traditional practices, but ethylene is the standard answer.

426. Symbol of Iron is__________?

• A. Na
• B. Fr
• C. Fe
• D. Zn

Explanation: Iron has the symbol Fe, derived from its Latin name ferrum. Na is sodium, Zn is zinc, and Fr is francium.

427. Carbon dioxide was discovered by_______?

• A. Niels Bohr
• B. Amedeo Avogadro
• C. Joseph Black
• D. None of Above

Explanation: Joseph Black identified carbon dioxide in the eighteenth century and called it fixed air. Bohr was a physicist, while Avogadro is associated with molecular theory and the mole concept.

428. Molasses is a byproduct of ______ Factory ?

• A. Fertilizer
• B. Cotton seed oil
• C. Sugar
• D. Banaspati Ghee

Explanation: Molasses is the thick, dark syrup left after sugar crystals are extracted from sugarcane or sugar beet juice. It is therefore a byproduct of the sugar industry.

429. Most soluble in water is:__________?

• A. Camphor
• B. Sulphur
• C. Common salt
• D. Sugar

Explanation: Sugar dissolves very readily in water because its polar groups interact strongly with water molecules. Common salt is also soluble, but generally less soluble than sugar under ordinary conditions.

430. Carbon,Diamond and Graphite are together called:___________?

• A. Allotrope
• B. Isomers
• C. Isomorphs
• D. Isotopes

Explanation: Diamond and graphite are different structural forms of the same element, carbon, so they are allotropes. Isotopes differ in neutron number, while isomers have different molecular structures.