2 0 g of hydrated copper sulphate gave on heating,1 2786 g of anhydrous salt calculate the number of molecules - Chemistry - Some Basic Concepts of Chemistry

Question

2 0 g of hydrated copper sulphate gave on heating,1 2786 g of
anhydrous salt calculate the number of molecules of water of
crystallisation per molecule of hydrated salt

Anita Dahiya · Accepted Answer

Heating the will lead to the evaporation of the water of
crystallization The mass of water evaporated can be obtained by
subtracting the mass of the residue obtained

From the question above,
mass of the copper sulfate crystal = 2 g
Mass of residue = 1 2786 g
Mass of water evaporated = 2gâˆ’1 2786g = 0 72
g

Lets assume that the number of molecules of water - x

The number of molecules of water, x, is obtained by using the
formula:
Mass of evaporated waterâ„Mass of crystal = Molar Mass
of evaporated waterâ„Molar Mass of crystal
Molar Mass of evaporated water = 18x
Molar Mass of crystal = (18x+160)
Therefore,
18xâ„(18x+160 )= 0 72â„2
2(18x) = 0 72(18x + 160)
36x = 12 96x + 115 2
36x-12 96x = 115 2
23 04x = 115 2
23 04xâ„23 04=115 2/23 04
x = 5
Therefore, the number of molecules of water, x, in the crystal is
5

2.0 g of hydrated copper sulphate gave on heating,1.2786 g of anhydrous salt.calculate the number of molecules of water of crystallisation per molecule of hydrated salt.