CBSE Class 10 Science 2017 · Paper 31/1/1 · Question 27

A student took four test tubes P, Q, R and S and filled about 8 mL of distilled water in each. After that he dissolved an equal amount of ${\text{Na}}_2{\text{SO}}_4$ in P, ${\text{K}}_2{\text{SO}}_4$ in Q, ${\text{CaSO}}_4$ in R and ${\text{MgSO}}_4$ in S. On adding an equal amount of soap solution and shaking each test tube well, a good amount of lather will be obtained in the test tubes :