All Free Chemistry MCQs with Answers

• A. 1%
• B. 10%
• C. 4%
• D. 2%

Explanation: When water is added to plaster of Paris, it undergoes a chemical reaction called hydration, forming gypsum.

• A. NaO2
• B. Na2O2
• C. Na2O
• D. Na2O3

Explanation: This is sodium peroxide, formed when sodium burns in excess air. Therefore,option b is the correct answer.

• A. CaCO3
• B. Ca(OH)2 . H2O
• C. Ca(OH)2
• D. CaSO4

Explanation: This is the correct formula for slaked lime, also known as calcium hydroxide. It's formed when calcium oxide (quicklime) reacts with water.

• A. Enlarged root system in plants
• B. Chlorophyll development in leaves
• C. Good yield of crops
• D. Control of pH of soil

Explanation: Sulfur can affect soil pH when it reacts with water to form sulfuric acid or sulfate ions, thereby influencing soil acidity.

• A. H2
• B. Na
• C. Cl2
• D. O2

Explanation: Hydrogen gas is produced at the cathode during the electrolysis of brine (sodium chloride solution) in Nelson's cell.

• A. Be
• B. Mg
• C. Ca
• D. Sr

Explanation: Beryllium is amphoteric, which means it can react with both acids and bases (alkalis).

• A. 800oC
• B. 600oC
• C. 1800oC
• D. 900oC

Explanation: This is the correct operating temperature of a Down's cell. The temperature is kept around 600°C to ensure that the electrolyte (a mixture…

• A. Dolomite
• B. Gypsum
• C. Calcite
• D. Asbestos

Explanation: The composition CaMg3(SiO3)4 corresponds to asbestos, a group of fibrous silicate minerals.

• A. KCl
• B. NaCl
• C. MgCl2
• D. SrCl2

Explanation: NaCl, is the correct answer as halite is the mineral name for sodium chloride.

• A. Be
• B. Ra
• C. Ba
• D. Rn

Explanation: Radon is not an alkaline earth metal; it is a noble gas. Radon is a radioactive, colorless, and odorless gas that is formed naturally as a…

• A. Acidic
• B. Basic
• C. Amphoteric
• D. None of these

Explanation: Beryllium oxide (BeO) exhibits amphoteric behavior, meaning it can react with both acids and bases.

• A. KNO3
• B. KNO2
• C. Na2B4O7
• D. Na2CO3 . H2O

Explanation: Potassium nitrate has the chemical formula KNO3, and it is commonly known as saltpetre or saltpeter.

• A. Gypsum
• B. Dolomite
• C. Calcite
• D. Epsom salt

Explanation: CaSO4 . 2H2O is commonly known as gypsum. It's a soft sulfate mineral composed of calcium sulfate dihydrate.

• A. H2
• B. Na
• C. Cl2
• D. O2

Explanation: During the electrolysis of brine in a diaphragm cell, hydrogen gas is indeed deposited at the cathode.

• A. Gypsum
• B. Dolomite
• C. Calcite
• D. Plaster of Paris

Explanation: CaSO4.1/2H2O is also known as Plaster of Paris.

• A. Down the Group
• B. Along the period
• C. Diagonally
• D. Only along the d-block

Explanation: As you go down the group, the period number increases, thus a new subshell is added.This leads to an increased shielding effect as more…

• A. Absorbs CO2 and increases O2 content
• B. Eliminates moisture
• C. Absorbs CO2
• D. Produces ozone

Explanation: Potassium superoxide (KO2) plays a vital role in environments like space and submarines by regenerating breathable air.

• A. F<K<Li
• B. F<LI<Na<K
• C. Li<Na<K<F
• D. Na<K<Li<F

Explanation: The correct order of atomic radii is F < Li < Na < K. Fluorine (F) has the smallest atomic radius due to its position on the extreme right…

• A. Ionisation energy
• B. Shielding effect
• C. Inert pair effect
• D. Both A. and B.

Explanation: The correct answer is Option D:Both A. and B.Atomic size increases down the group due to (i) Increase in the number of shells, and (ii)…

• A. An acid
• B. A base
• C. A metallic anhydride
• D. A basic anhydride

Explanation: Metal oxides, such as calcium oxide, are known as basic anhydrides because they react with water to produce bases.