ECAT Chemistry — Experimental Techniques

How Experimental Techniques is tested

Across the 7 ECAT past papers on ParhaiKrlo, Experimental Techniques accounts for 4 questions. It appears in 3 of them, about 1.3 questions a paper. The heaviest was ECAT Past Paper 02, with 2 questions, and the most recent is ECAT Past Paper 07, with 1.

Experimental Techniques MCQs from the ECAT past papers

Try each one before opening the answer. Each comes with a short explanation.

1. Q1 · ECAT Past Paper 07 · Experimental Techniques

   The basic principle of crystallization is:

   • A.The solute should be completely soluble in the solvent at room temperature so that it is thrown out as crystals at any temperature
   • B.The solute should be soluble in a suitable amount of solvent at high temperature, and the excess is thrown out as crystals when it is cooled
   • C.The solute should not be soluble in the solvent at any temperature
   • D.The solubility of the solute should not be affected by temperature
   Show answer

   Answer: B. The solute should be soluble in a suitable amount of solvent at high temperature, and the excess is thrown out as crystals when it is cooled — A good crystallization solvent dissolves the solute when hot but not when cold, so crystals form on cooling.

2. Q2 · ECAT Past Paper 02 · Experimental Techniques

   In solvent extraction, once the solute has passed into the ether layer, it is recovered by ______ the ether.

   • A.Boiling
   • B.Evaporating
   • C.Heating
   • D.Mixing with H₂O
   Show answer

   Answer: B. Evaporating — Ether is very volatile, so it is simply evaporated off, leaving the solute behind.

3. Q3 · ECAT Past Paper 01 · Experimental Techniques

   In paper chromatography, the comparative rate at which a solute moves depends on the Rf value of the:

   • A.Solute
   • B.Solution
   • C.Solvent
   • D.None
   Show answer

   Answer: A. Solute — Rf = distance moved by the solute ÷ distance moved by the solvent; each solute has its own Rf.