Question

Calculate the mass of Calcium that will contain the same number of atoms as are present in 3.2 gm of Sulphur. [Atomic masses : * = 32, Ca = 40]

Answer 1

32 gm of sulphur contain = 6.023 x 1023 atoms

3.2 gm of sulphur contain = (6.023 x 1023)/32 x 3.2 = 6.023 x 1022

Now, 6.023 x 1023 atom of calcium have mass = 40 g

6.023 x 1022 atoms of calcium have mass = 40/(6.023 x 1023) x (6.023 x 1022) = 4 g

Hence, the mass of calcium is 4 g.