Q. 334.2( 62 Votes )

Calculate the number of atoms in each of the following:

(i) 52 moles of Ar

(ii) 52 u of He

(iii) 52 g of He.

Answer :

(i) According to Avogadro’s Law,

1 mole of Argon 6.023×1023 atoms of Argon


So, 52 moles of Argon X atoms of Argon


X =52×6.023×1023


=3.13196×1025


Therefore in 52 moles of Argon 3.13196×1025 atoms are present.


(ii) Atomic Mass of Helium [He] = 4 u

This means that mass of one atom of Helium is = 4 u

So, Number of atom of Helium contained in 52 u = 52/4= 13 atoms

Therefore, in 52 u of Helium 13 atoms are present.


(iii) Atomic Mass of Helium [He] = 4 u

Number of Moles of Helium in 52 g = 52/4= 13 moles

So, Number of atoms in 52g of Helium [He] = 13×6.023×1023= 7.8299×1024


Therefore, in 52 g of Helium 7.83×1024 atoms are present.

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