Question

Calculate the percentage of water of crystallization in \[CuS{{O}_{4}}.5{{H}_{2}}O\] (H =1, O =16, S = 32, Cu = 64).

Answer 1

Hint: Copper sulphate is hygroscopic in nature. When copper sulfate it reacts with water it forms a hydrated form of the salt. Copper sulphate reacts with five water molecules and forms pentahydrate copper sulphate. The molecular formula of copper sulphate pentahydrate is\[CuS{{O}_{4}}.5{{H}_{2}}O\].

Complete step by step answer:
-In the question, it is given that
The atomic mass of Hydrogen =1
The atomic mass of oxygen = 16g
The atomic mass of sulphur = 32g
The atomic mass of copper = 64g
-In the chemical formula\[CuS{{O}_{4}}.5{{H}_{2}}O\], it contains one copper atom, one sulphur atom, nine oxygen atoms, and ten hydrogen atoms.
-Then the Molar mass of \[CuS{{O}_{4}}.5{{H}_{2}}O=64+32+(9\times 16)+(10\times 1)=250g\]
-Five water molecules contain (\[5{{H}_{2}}O\]), ten hydrogen atoms and five oxygen atoms.
-So, Molar mass of five water molecules (\[5{{H}_{2}}O\])= 90g
-Now we have to calculate the percentage of water of crystallization in \[CuS{{O}_{4}}.5{{H}_{2}}O\].
25 g of \[CuS{{O}_{4}}.5{{H}_{2}}O\]contains 90 g of water of crystallization = \[\dfrac{90}{250}\times 100=36%\]

Therefore the percentage of water of crystallization in \[CuS{{O}_{4}}.5{{H}_{2}}O\]is 36%.

Additional information:
-Copper sulfate (\[CuS{{O}_{4}}\]) is corrosive to the skin and eyes.
-It is used as an activator in the froth flotation process of cobalt, gold and lead.
-It is used in Demolition of algal blooms in water reservoirs.

Note: When water is added to the anhydrous copper sulphate (\[CuS{{O}_{4}}\]), it converts into the pentahydrate form (\[CuS{{O}_{4}}.5{{H}_{2}}O\]), but still, it retains its blue colour, and it is also known as blue vitriol.