All Free Everyday Science MCQs with Answers

461. Proton number is denoted by symbol __________ ?

• A. M
• B. Z
• C. P
• D. A

Explanation: The atomic number, or proton number, is represented by Z and equals the number of protons in the nucleus. A represents mass number, which includes protons and neutrons.

462. When an acid reacts with a metal, which one of the following gas is usually liberated?

• A. Ammonia Gas
• B. Chlorine
• C. Oxygen
• D. Hydrogen gas

Explanation: Most metals react with dilute acids to form a salt and release hydrogen gas, producing bubbles. Strong oxidising acids such as concentrated nitric acid are exceptions, but hydrogen is the usual answer.

463. Permanent hardness of water due to sulphate of metals can be destroyed by the use of ________ ?

• A. Zeolites
• B. Sulphonides
• C. Lime
• D. Nitrates

Explanation: Zeolites remove calcium and magnesium ions by exchanging them for sodium ions, so they can eliminate permanent hardness caused by sulphates and chlorides. Lime is mainly used for certain forms of temporary hardness.

464. What is the Chemical formula of Zinc Hydroxide _________ ?

• A. Zn(OH)2
• B. ZNO2
• C. Zn2(OH)3
• D. ZnOH

Explanation: Zinc forms Zn²⁺ ions and hydroxide forms OH⁻ ions, so two hydroxide ions are needed to balance one zinc ion. The formula is therefore Zn(OH)₂.

465. The valency of carbon Atom is __________ ?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Carbon has four electrons in its outer shell and generally forms four covalent bonds to complete that shell. Its usual valency is therefore 4.

466. Second name of ethyl alcohol is___________?

• A. Ethene
• B. Ethanol
• C. Propyle
• D. none

Explanation: Ethyl alcohol is the common name for ethanol, whose chemical formula is C₂H₅OH. Ethene is a different compound and is an unsaturated hydrocarbon.

467. Which one of the following non-metals is not a poor conductor of electricity?

• A. Sulphur
• B. Selenium
• C. Bromine
• D. Phosphorus

Explanation: Selenium is a semiconductor, so it conducts electricity better than typical non-metals such as sulphur, bromine, and phosphorus. It is therefore not classed as a very poor conductor in the usual sense.

468. Which one of the following is not a radioactive element ?

• A. Cadmium
• B. Thorium
• C. Radium
• D. Uranium

Explanation: Cadmium is a stable, non-radioactive element, whereas thorium, radium and uranium are naturally radioactive because their nuclei undergo spontaneous decay.

469. Which of the following is used in beauty parlours for hair setting?

• A. Silicon
• B. Chlorine
• C. Sulphur
• D. Phosphorus

Explanation: Sulfur-containing compounds are used in hair treatments because they affect the disulfide bonds in keratin, helping reshape and set hair. Silicon, chlorine and phosphorus are not the usual answer for this traditional hair-setting use.

470. Which of the following is not a chemical reaction ?

• A. Burning of coal
• B. Conversion of water into steam
• C. Digestion of food
• D. Burning of paper

Explanation: Changing water into steam is a physical change because only its state changes and no new substance forms. Burning and digestion are chemical reactions that produce new substances.