A non-volatile solid solute may be separated from a solution by which of the following processes? I. Evaporation II. Crystallization Select the correct answer using the code given below.
- A.I only
- B.II only
- C.Both I and II
- D.Neither I nor II
Correct answer
Explanation
The correct answer is C, both I and II. A solid that does not vaporise stays behind when the solvent is removed, whether the solvent is boiled off or the solid is made to crystallise out.
In evaporation the solution is heated until the solvent turns to vapour and escapes, leaving the non-volatile solute as a residue, as when common salt is left after sea water dries. Crystallisation goes a step further: a hot saturated solution is cooled slowly so that pure crystals of the solute form and can be filtered off. It is preferred when the solid would decompose on strong heating, as with sugar, or when a purer product is wanted, as with copper sulphate or alum.
A is wrong because crystallisation also separates the solute.
B is wrong because simple evaporation works too.
D is wrong because both methods are standard ways to recover a dissolved solid.
Exam tip: evaporation leaves a residue; crystallisation gives pure crystals and avoids decomposing the solid.
Practice Questions
View allA charged particle moves through a magnetic field B with a velocity v. Which one of the following statements is true for the force (F) experienced by the particle?
- A.F is maximum when v and B are parallel to each other.
- B.F is maximum when v and B are anti-parallel to each other.
- C.F is maximum when v and B are perpendicular to each other.
- D.The force F is independent of the angle between v and B.
Show answer
The magnetic force depends on the sine of the angle between velocity and field, and sin 90° is the largest value.
Read the full explanation →In Sun-Earth system, the Sun, the Earth and the Lagrange point L4 form :
- A.an isosceles triangle
- B.an equilateral triangle
- C.a straight line
- D.a scalene triangle
Show answer
L4 lies on Earth's orbit 60° ahead of the Earth, so it is as far from the Sun as from the Earth.
Read the full explanation →Which one of the following is the most characteristic property of an element?
- A.Density
- B.Boiling point
- C.Mass number
- D.Atomic number
Show answer
The number of protons in the nucleus defines an element, and no two elements share it. The atomic number (Z) is the number of protons in an atom's nucleus, and in a neutral atom it also equals the number of electrons, which decide chemical behaviour.
Read the full explanation →After using for some time, big transformers get heated up. This is due to the fact that
1. current produces heat in the transformers
2. hysteresis loss occurs in the transformers
3. liquid used for cooling gets heated
Select the correct answer using the code given below.
- A.1 only
- B.2 and 3 only
- C.1 and 2 only
- D.1, 2 and 3
Show answer
A transformer heats up because of energy lost inside it: heat from current in the windings and hysteresis loss in the iron core.
Read the full explanation →Statement I : A person may suffer from tuberculosis if she/he frequently visits crowded place.
Statement II : Bacteria of tuberculosis spread through droplets by sneezing or coughing.
- A.Both the statements are individually true and Statement II is the correct explanation of Statement I
- B.Both the statements are individually true but Statement II is not the correct explanation of Statement I
- C.Statement I is true but Statement II is false
- D.Statement I is false but Statement II is true
Show answer
Both statements are true, and the airborne spread of the TB bacterium is exactly why crowded places raise the risk.
Read the full explanation →