All Free Chemistry MCQs with Answers

• A. It is used in the manufacture of buses, trains and aeroplanes
• B. It is used in making of utensils and window frames
• C. It is used in thermite welding
• D. It is very heavy metal and used to make balance

Explanation: The correct answer is Option D. Aluminum is known for being a lightweight metal, not a heavy one.

• A. Ca, Mg, K, Na
• B. Ca, K, Na, Mg
• C. K, Na, Ca, Mg
• D. Mg, K, Na, Ca

Explanation: Option C is correct because it arranges the metals in order of their reactivity with water or steam, starting with the most reactive.The…

• A. Sr does not burn in air
• B. Sr does not react with steam
• C. SrCO3 decomposes at a lower temperature than CaCO3
• D. Sr(OH)2 is dehydrated to the oxide on being heated

Explanation: The correct answer is Option D. Strontium hydroxide (Sr(OH)2) indeed undergoes dehydration to form strontium oxide (SrO) when heated.

• A. There is increase in the nuclear charge of the alkaline earth metal
• B. There is decrease in the nuclear charge of the alkaline earth metal
• C. There is no change in the nuclear charge
• D. None of the above

Explanation: As the nuclear charge increases, it requires more energy to remove an electron (ionization energy).

• A. Sodium sulphate
• B. Potassium sulphate
• C. Zinc sulphate
• D. Barium sulphate

Explanation: Option D, Barium sulphate, is the correct answer because it has a very low solubility in water, unlike the other options which are…

• A. Ca
• B. Cr
• C. Both of the above
• D. None of the above

Explanation: Option D, "None of the above," is correct because the element caesium (Cs) does not bear resemblance to either calcium (Ca) or chromium…

• A. It exists as AlCl2 molecule
• B. It is not easily hydrolysed
• C. It sublimes at 100oC under vacuum
• D. It is a strong Lewis base

Explanation: Anhydrous aluminum chloride does not readily react with water to undergo hydrolysis.

• A. It is a non-metal and other elements are metals
• B. It is a semi-conductor and other elements are conductors
• C. Its ionization energy is higher than other elements
• D. All of these

Explanation: The correct answer is Option D: 'All of these.' Boron stands out in Group III-A as a non-metal, a semiconductor, and having a higher…

• A. Decreases
• B. Increases
• C. Remains unchanged
• D. First decreases then increases

Explanation: Option B, 'Increases,' is correct because electrical conductivity generally increases from Beryllium (Be) to Radium (Ra) within the…

• A. K
• B. Na
• C. Cs
• D. Rb

Explanation: Superoxide (O2-) is formed when an alkali metal donates an electron to an oxygen molecule.

• A. Acidic
• B. Amphoteric
• C. Basic
• D. Neutral

Explanation: The oxides of s-block elements are generally basic in nature. This is because s-block elements tend to lose electrons to form positive…

• A. Belong to the same period
• B. Belong to the same group
• C. Are oxidizing agents
• D. Are reducing agents

Explanation: Option A is correct because both Aluminium (Al) and Sulphur (S) belong to the same period on the periodic table.

• A. Their chlorides are ionic solids
• B. Covalent bond is found in most of the compounds
• C. They are in the same period of the periodic table
• D. They are in the same group of the periodic table

Explanation: The correct answer is Option C. Na, Si, and S all belong to the same period of the periodic table, which is the third period.

• A. AlI3
• B. AlCl3
• C. AlBr3
• D. AlF3

Explanation: Aluminum iodide (AlI3) is predominantly covalent due to the smaller electronegativity difference between aluminum and iodine, allowing for…

• A. Sodium
• B. Aluminium
• C. Silicon
• D. Phosphorus

Explanation: The correct answer is A. Sodium.When an element from the third period (Na to S) is boiled in chlorine, it forms a compound called sodium…

• A. BaO...Basic oxide
• B. Ga2O3.....Amphoteric oxide
• C. N205...Basic oxide
• D. BeH2...Intermediate hydride

Explanation: N2O5 is an acidic oxide, not a basic oxide. An acidic oxide reacts with water to form an acid.

• A. Na2O
• B. MgO
• C. Al2O3
• D. SO3

Explanation: Option A is correct because sodium oxide (Na2O) dissociates in water to form hydroxide ions, making the solution strongly basic.

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: Option A is correct because beryllium is located in period 2 of the periodic table.

• A. Aluminium
• B. Diamond
• C. Graphite
• D. Silicon

Explanation: Silicon is the correct answer as it is a semiconductor with properties that allow it to be used in electronic devices.

• A. It has a high value of refractive index
• B. All the valence electrons of each carbon atom are involved in bonding
• C. It is a giant covalent structure
• D. It is a crystalline allotrope of carbon

Explanation: Diamond is a form of carbon with a giant covalent structure, where each carbon atom forms four strong covalent bonds, creating a rigid…