Question

what mass of Ca will have the same number of atoms as in 3.2 g of S (ans:- 4g)

Answer 1

We know that, 

Weigh of 1 mole of an element = Atomic mass of the element

Number of atoms in 1 mole of an element = 6.023 x1023.

So, 32 g of S contains 6.023x1023 atoms.

Therefore, 3.2 g of S will contain ( 6.023x1023x 3.2)/32 = 6.023x1022 atoms of S.

Now, weight of  6.023x1023 atoms of Ca is 40 g.

Thus, weight of  6.023x1022 atoms of Ca will be ( 6.023x1022 x 40) /  6.023x1023 = 4 g.