Question

Copper sulphate crystals contain 25.45% of copper and 36.07% of water. If the law of definite proportion is true ; then calculate the mass of copper required to obtain 40 g of crystalline copper sulphate.

Answer 1

According to thy given values 
100 gram or crystalline cuSO4 sulphate needs 25.45 gram of Cu 
hence 40 gram of crystal copper sulphate will need 
25.45x40/ 100 = 10.18 gram of Cu
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