JKSSB Sub Inspector 2022 Q44 solved answer

JKSSB Sub Inspector - Science & Technology - 2022

View full paper: JK PSI 2022

Question

Which of the following when added to pure water usually increases its surface tension?

  1. A. Detergent
  2. B. Sodium chloride
  3. C. Kerosene oil
  4. D. Phenyl

Answer

Correct option: B - Sodium chloride

Surface tension is caused by intermolecular cohesive forces in a liquid. Adding sodium chloride (NaCl) to pure water increases its surface tension because the ions (Na+ and Cl-) increase the electrostatic attraction among water molecules. Detergents and soaps decrease surface tension (they are surfactants). Kerosene oil and phenyl also lower surface tension as organic compounds that disrupt water's hydrogen bonding network. NaCl is one of the few common solutes that actually raises water's surface tension.