Question

Calculate the number of atoms in the following (at. mass of Ar = 40)
(i) 4 g of Ar (ii) 40 u of Ar (iii) 4 mol of Ar (iv) 40 g of Ar.​

Answer 1

Answer:

(i) 1 mole of Ar =6.022×10

23

atoms of Ar

52 mol of Ar=52×6.022×10

23

atoms of Ar

=3.131×10

25

atoms of Ar

(ii) Atomic mass of He = 4amu

Or

4amu is the mass of He atoms = 1

Therefore 52 amu is the mass of He atoms=0.25×52=13 atoms of He

(iii) Gram atomic mass of He = 4g

Or

4g of He contains =6.022×10

23

atoms

Therefore 52 g of He contains=

4×52

6.022×10

23

=7.83×10

24

atoms