Question

(a) What is blue Vitriol? How is it useful in detecting the presence of water vapour?

(b) When a magnetic field is applied, certain substances are attracted by the applied field. Those are called paramagnetic substances. Which is more paramagnetic Mn²⁺ or Cu²⁺? Why?

Answer 1

(a) CuSO₄ 5H₂O is known as blue vitriol. Anhydrous copper sulphate is used for detecting the presence of water vapour. Water vapour converts white anhydrous copper sulphate to blue hydrated copper sulphate.

(b) As the number of unpaired electrons increases, paramagnetism increases.
Mn → [Ar] 4s² 3d⁵ and Mn²⁺ → 3d⁵
Cu → [Ar] 4s¹ 3d¹⁰ and Cu²⁺ →3d⁹ 

Mn²⁺ contains five unpaired d-electrons and
Cu²⁺ contains only unpaired electron.
∴ Mn²⁺ is more paramagnetic than ²⁺.