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.