Question

A student has a piece of copper sulfate (CuSO₄) crystal. Explain the method of calculating the number of CuSO₄ molecules in that crystal. 

(Given atomic masses : Copper = 40, Sulfur = 32 and Oxygen = 16)

Answer 1

Molecular formula of copper sulfate = CuSO₄ 

Gram molecular mass of CuSO₄ 

= 40+32 + (16 × 4) 

= 72 + 64 = 136 grams 

Gram molecular mass of CuSO₄ 

= 1 mole = 6.023 × 10²³ molecules 

If the students has 136 grams of CuSO₄ then the number of molecules in that crystal will be 6.023 × 10²³.