Which of the following varies with temperature ?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Molarity (M)
Molarity is moles of solute per litre of solution. The volume of a liquid changes with temperature but its mass does not, so volume-based terms such as molarity change with temperature, while mass-based terms (mass percentage, molality, ppm) do not.
Why the other options are incorrect
Option (1) Mass percentage (w/w) — Incorrect. Mass percentage is a ratio of masses, so it does not change with temperature.
Option (3) Molality (m) — Incorrect. Molality sounds similar, but it is moles of solute per kilogram of solvent. It is based on mass, so it does not change with temperature.
Option (4) Parts per million (ppm) — Incorrect. Parts per million is usually a ratio of masses, so it does not change with temperature.
NCERT (2026-27 edition):
Expressing Concentration of Solutions – …
