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Answer» (i) Hydrated copper sulphate – CuSO4.5H2O Anhydrous copper sulphate – CuSO4 Solutions Activity : (a) Heat a few crystals of copper sulphate in a dry boiling tube. (b) Add 2 – 3 drops of water on the sample of copper sulphate obtained after heating. Water is removed and salt turns white. If crystals are moisten again with water, blue colour reappears. Water of crystallisation is fixed number of water molecules present in one formula unit of a salt. Five water molecules are present in one formula unit of copper sulphate. (ii) Calcium sulphate hemihydrate — CaSO4.½H2O (Plaster of paris) Calcium sulphate dihydrate — CaSO4.2H2O (Gypsum) OR (i) Chemical name — Sodium carbonate decahydrate Formula — Na2CO3.10H2O (ii) NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3 2NaHCO3 → Na2CO3 + CO2↑ + H2O Na2CO3 + 10H2O → Na2CO3.10H2O (iii) It is a basic salt because when dissolved in water, it gives a strong base NaOH. It is used as a cleaning agent, in paper and glass industry.
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