Question

What are the number of molecules of water in CuSO4•5H2O, if the weight of oxygen in it is 36 grams?

(a) 3.25 X 10^23

(b) 5.25 X 10^23

(c) 7.52 X 10^23

(d) 9.52 X 10^23

I got this question during an interview.

Question is taken from The Mole in division Moles, Density & Concentration of Basic Chemical Engineering

Answer 1

Right choice is (c) 7.52 X 10^23

The best I can explain: Number of moles of oxygen = 36/16 =2.25, => number of moles of CuSO4•5H2O = 2.25/9 = 0.25, => number of molecules of water = 0.25*5*(6.022 X 10^23) = 7.52 X 10^23.