Question

How many grams of CuSO₄*5H₂O should be dissolved in a volume of 500.0 mL to make 8.00 mM Cu²⁺?

Answer 1

Given Molarity of Cu²⁺ = 8.00 mM = 8.00x10^-3 M

Volume of the solution is , V = 500.0 mL = 0.50 L

We know that Molarity , M = Number of moles / Volume of solution in L

               8.00x10^-3 M = n / 0.50 L

      n = 4.0x10^-3 mol

Molar mass of CuSO₄*5H₂O

        = At.mass of Cu + At.mass of S + (4xAt.mass of O) + 5[(2xAt.mass of H)+At.mass of O]

        = 63.5+32+(4x16)+5[(2x1)+16]

        = 249.5 g/mol

We know that number of moles , n = mass/molar mass

So mass of CuSO₄*5H₂O , m = number of moles x molar mass

                                           = 4.0x10^-3 mol x 249.5 g/mol

                                          = 0.998 g

Therefore the mass of CuSO₄*5H₂O is 0.998 g