Chemistry · Chemical principles involved in the qualitative salt analysis Cations: Pb2+, Cu2+, Al3+, Fe3+, Zn2+, Ni2+, Ca2+, Ba2+, Mg2+, NH4+
A student takes about of distilled water in four test tubes marked and He then d
A student takes about \( 4 \mathrm{ml} \) of distilled water in four test tubes marked \( P, Q, R \) and \( S . \) He then dissolves in each test tube, an equal amount of various salts, viz. sodium sulphate in \( P, \) potassium sulphate in \( Q, \) calcium sulphate in \( R \) and magnesium sulphate 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 \( S \)
Step-by-step solution
Soap reacts with calcium and magnesium ions (from CaSO4 and MgSO4) to form insoluble scum, reducing lather. Sodium and potassium ions (from Na2SO4 and K2SO4) do not cause hardness, so lather forms well in test tubes P and Q.
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