P-Block Elements: NEET MCQ practice

Answer: A. Aluminium

Cryolite (Na3AlF6) is a key mineral used as a flux in the electrolytic extraction of aluminium from its chief ore bauxite. It lowers the melting point of alumina, making the process efficient. The other ores listed – zinc (sphalerite), iron (haematite), copper (copper pyrites) – are not associated with cryolite.

Answer: C. Gold

Gold is the least reactive metal among the options and occurs native in nature because it does not readily form compounds. Silver and copper can occur native but are also found in combined forms, while sodium is highly reactive and never found free.

Answer: D. Both magnesium and Calcium

Dolomite is a common mineral with formula CaMg(CO₃)₂, containing both calcium and magnesium. The correct option is (d) because dolomite contains both elements. Other options list only one, which would be incorrect minerals (like bauxite for aluminium, magnesite for magnesium, calcite for calcium).

Answer: D. Ionisation enthalp

In the halogen group (Group 17), ionization enthalpy decreases down the group because atomic size increases, reducing the effective nuclear pull on the outermost electron, making it easier to remove. Boiling point and density increase down the group due to increasing molecular size and van der Waals forces. Electropositive nature actually increases slightly down the group, but halogens are strongly electronegative overall, so it's not a typical property for them.

Answer: B. cryolite

Cryolite (Na₃AlF₆) is a fluoride ore of aluminium used in its extraction. Carnallite is a chloride ore of potassium and magnesium, and Chile saltpetre is sodium nitrate. Hence, only cryolite fits the description.