solute-solvent-and-solution MCQs for UPSC Prelims

30 practice questions on solute-solvent-and-solution from the The Amazing World of Solutes, Solvents, and Solutions section of the UPSC Prelims syllabus. 30 come with a written explanation. Try the sample set below - the answer stays hidden until you ask for it.

9 Easy 15 Medium 6 Hard

Sample questions

Q1
hard

Assertion (A): Sugar can be separated from a sugar solution by pouring the solution through filter paper. Reason (R): Dissolved sugar particles are much smaller than the pores of filter paper.

  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: D - A is false, but R is true

A is false, because the sugar passes straight through the paper along with the water and nothing is left behind. R is true, and it is exactly the reason why filtration fails here. A false assertion paired with a true reason gives the fourth choice.

Q2
easy

Sugar is stirred into a glass of water until it has all dissolved. A sip taken from the top and a sip taken from near the bottom will taste

  1. A different each time the glass is used
  2. B sweeter at the top
  3. C sweeter at the bottom
  4. D equally sweet, because a solution is uniform throughout
Show answer and explanation

Correct answer: D - equally sweet, because a solution is uniform throughout

In a solution the solute spreads evenly, so every part has the same composition and the same sweetness. Dissolved sugar does not sink to the bottom, and nothing pushes it upwards either. A uniform mixture gives the same result every time, so the last option is wrong.

Q3
medium

Minerals present in the soil reach the leaves of a plant because

  1. A water dissolves the minerals and carries them up the plant
  2. B water pushes solid grains of mineral up the stem
  3. C minerals change into water inside the root
  4. D grains of mineral float on the surface of soil water
Show answer and explanation

Correct answer: A - water dissolves the minerals and carries them up the plant

Roots take in water in which soil minerals are already dissolved, and this solution travels up to the leaves. Solid grains cannot enter the root or move up its narrow tubes, so floating or pushing does not happen. Minerals do not turn into water; they simply stay dissolved in it.

Q4
easy

Brass is a solid solution made by mixing

  1. A aluminium and silver
  2. B iron and carbon
  3. C copper and zinc
  4. D copper and tin
Show answer and explanation

Correct answer: C - copper and zinc

Brass is made by melting copper with zinc and letting the mixture set as one uniform solid. Copper with tin gives bronze and iron with carbon gives steel, so those options name different alloys. Aluminium with silver is not the recipe for brass.

Q5
medium

Consider these statements. Statement I: Filtration separates an insoluble solid from a liquid. Statement II: Filtration separates a dissolved solid from its solvent.

  1. A Only Statement I is correct
  2. B Both statements are correct
  3. C Both statements are wrong
  4. D Only Statement II is correct
Show answer and explanation

Correct answer: A - Only Statement I is correct

Filtration holds back particles that are too large to pass through the pores, so it works for insoluble solids such as sand and Statement I is correct. Dissolved particles are far too small to be held back, so Statement II is wrong; evaporation is needed for that job.

Q6
medium

A shopkeeper stirs $20\ \text{g}$ of citric acid into $500\ \text{g}$ of water to make a cold drink. Which statement about this solution is correct?

  1. A Citric acid is the solvent, as it was added later
  2. B Water is the solute, as it is a liquid
  3. C Water is the solute, as it is present in the larger amount
  4. D Citric acid is the solute, as it dissolves and is present in the smaller amount
Show answer and explanation

Correct answer: D - Citric acid is the solute, as it dissolves and is present in the smaller amount

The component present in the larger amount and doing the dissolving is the solvent, which here is water. Citric acid dissolves in it and is the smaller part, so it is the solute. The second and fourth options call water the solute, which reverses the rule. The order of adding does not decide which one is the solvent.

Q7
medium

The correct way to get solid salt back from a salt solution is

  1. A filtering the solution
  2. B evaporating the water
  3. C sieving the solution
  4. D adding more water to the solution
Show answer and explanation

Correct answer: B - evaporating the water

Heating the solution or leaving it in the Sun drives the water away as vapour, and the salt is left behind as a solid. Filtration and sieving cannot separate a dissolved solid, because its particles pass straight through. Adding more water only makes the solution more dilute.

Q8
easy

Which of these substances dissolves readily in water?

  1. A Chalk powder
  2. B Common salt
  3. C Fine sand
  4. D Mustard oil
Show answer and explanation

Correct answer: B - Common salt

Common salt dissolves in water and gives a clear solution. Sand and chalk powder stay as separate particles that settle down and can be filtered out, so they are insoluble. Mustard oil does not dissolve either; it floats and forms a separate layer.

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