All Free Everyday Science MCQs with Answers

381. Sodium Carbonate is commonly called ________?

• A. Plaster of Paris
• B. Washing Soda
• C. Common Salt
• D. None of these

Explanation: Sodium carbonate decahydrate, Na₂CO₃·10H₂O, is commonly called washing soda. Plaster of Paris is calcium sulfate hemihydrate, and common salt is sodium chloride.

382. For burning, which agent is necessary?

• A. Oxygen
• B. Hydrogen
• C. Carbon
• D. Fire

Explanation: Ordinary burning is combustion, which requires an oxidizing agent, normally oxygen from the air. Hydrogen and carbon may be fuels, but they are not the necessary supporting agent.

383. Which element is called earth maker?

• A. Oxygen
• B. Silicon
• C. Carbon
• D. Hydrogen

Explanation: Silicon is called an earth-maker because silicate minerals containing silicon form a major part of the Earth's crust. Oxygen is more abundant by mass, but the nickname specifically points to silicon's role in making rocks and minerals.

384. Which group of compounds constitute carbohydrates?

• A. Sugar and proteins
• B. Starch and proteins
• C. Starch and sugar
• D. None of these

Explanation: Carbohydrates include simple sugars and complex polysaccharides such as starch. Proteins are a separate class of biomolecules, so combinations containing proteins are not correct.

385. Characteristic odour of garlic is due to?

• A. A fluorine compoune
• B. A sulphur compound
• C. A chlorine compound
• D. None of these

Explanation: Garlic’s characteristic smell comes mainly from sulfur-containing compounds such as allicin, released when garlic is cut or crushed. Fluorine and chlorine compounds are not responsible for its normal odour.

386. Which has highest fuel value?

• A. Charcoal
• B. Gasoline
• C. Hydrogen
• D. None of these

Explanation: Hydrogen has the highest calorific value per unit mass among common fuels, releasing about 120 MJ per kilogram when burned. Its high fuel value is why it is considered an important future fuel.

387. Homologous means?

• A. Same Chemical Properties
• B. Same Chemical Numbers
• C. Different Chemical Properties
• D. Different Chemical Numbers

Explanation: Members of a homologous series have the same functional group and therefore similar chemical properties, while successive members differ by a CH₂ unit. They do not have identical chemical formulas or molecular numbers.

388. Unit of specific gravity is?

• A. Pascal
• B. No unit
• C. Mass/volume
• D. None of these

Explanation: Specific gravity is the ratio of a substance’s density to the density of a reference substance, usually water, so the units cancel. It is therefore a dimensionless quantity.

389. Which of the following is a transition element?

• A. Cl
• B. Cu
• C. S
• D. None of these

Explanation: Copper, Cu, is a transition element because it has a partially filled d subshell in its atom or common ions. Chlorine and sulfur are p-block nonmetals.

390. Melting Point of Tungsten is?

• A. 1000 C
• B. 2000 C
• C. 3000 C
• D. 4000 C

Explanation: Tungsten melts at approximately 3422°C, one of the highest melting points of any metal. Among the given approximate choices, 3000°C is the closest.