Match List I with List II

Choose the correct answers from the options given below:

A-II, B-III, C-IV, D-I

The correct answer is option 2. A-II, B-III, C-IV, D-I

To understand the matching of crystal systems to compounds, let's look at each crystal structure type and the compounds that typically exhibit them:

A. Triclinic System:

K₂Cr₂O₇ (Potassium dichromate) crystallizes in a triclinic system, which is the least symmetrical of all crystal systems. Triclinic crystals have three unequal axes, none of which intersect at 90° angles. Potassium dichromate’s structure aligns with this low symmetry.

B. Monoclinic System:

Na₂SO₄·10H₂O (Sodium sulfate decahydrate) crystallizes in the monoclinic system. In monoclinic crystals, two axes intersect at 90°, while the third is inclined. This system is often seen in hydrated salts, like sodium sulfate decahydrate, due to the arrangement of water molecules around the sodium ions, which reduces symmetry.

C. Rhombohedral System:

CaCO₃ (Calcium carbonate) in the form of calcite is rhombohedral. Rhombohedral (or trigonal) crystals have three equal axes that are inclined at equal angles that are not 90°. Calcite’s structure is rhombohedral, giving it unique cleavage planes that are characteristic of rhombohedral crystals.

D. Orthorhombic System:

BaSO₄ (Barium sulfate) crystallizes in the orthorhombic system. In orthorhombic crystals, all three axes are of different lengths but intersect at 90° angles. Barium sulfate’s crystalline arrangement falls under the orthorhombic category, consistent with its orthogonal but unequal axes.

This is why the correct answer is A-II, B-III, C-IV, D-I.