Question

A student takes about 4 ml of distilled water in 4 test tubes marked P,Q,R and S.He then added in each test tube an equal amount of one salt in one test tube,namely sodium sulphate in P, pottasium sulphate in Q , calcium in R and magnesium sulpahte in S. After that he adds an equal amount of soap solution in each test tube.On shaking each of these test tubes well,he observes a good amount of lather(foam) in the test tube marked:-

(a)P and Q
(b)Q and R
(c)P,Q and S
(d)P,R and S

State the reason

Answer 1

Answer is (a) P and Q

soap will not form lather in the presence of calcium and magnesium. They make the water hard...

It forms lather in P & Q...

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Answer 2

(d) P, R and S.

Because soap reacts with them to form lather.