Question

Crystallization is primarily used to:

• A. Increase reaction rate
• B. Separate solids based on density
• C. Purify solids from solution
• D. Reduce particle size

Hint:

Logic Tip: Think of making rock candy. You dissolve sugar (solute) in hot water (solvent) and let it cool. Pure sugar crystals grow on the stick, leaving any food coloring or impurities in the water. You are "purifying the solid from the solution."

Answer 1

The Correct Option is C

Concept:
Crystallization is a critical unit operation used to produce high-purity solid products from a liquid mixture by manipulating solubility.

Step 1: The process begins with an impure liquid solution, where the desired solid substance (solute) is completely dissolved in a liquid (solvent) alongside unwanted impurities.

Step 2: By either cooling the solution or evaporating some of the solvent, the solution is forced into a state where it contains more dissolved solid than it can naturally hold (supersaturation).

Step 3: To relieve this unstable state, the excess dissolved solute begins to solidify, forming highly ordered, rigid geometric structures called crystals.

Step 4: Because a crystal lattice is highly structured, it typically "rejects" molecules that don't perfectly fit its shape. Therefore, the newly formed solid crystals are extremely pure, leaving the impurities behind in the remaining liquid (mother liquor).

Step 5: * Increasing reaction rate relates to catalysis/temperature. * Separating based on density is sedimentation or centrifugation. * Reducing particle size is milling/crushing.

Step 6: Therefore, the primary industrial purpose of crystallization is to produce pure solid products from an impure liquid solution.