# calculate the number of atoms in each of the following (i)52 moles of Ar(ii)52u of He (iii)52d of He

(1) 52 moles of Ar

We Know

1 mole of Ar = 6.022 X 1023 atoms of Ar

Therefore 52 moles of Ar = 6.022 X 1023 X 52 atoms of Ar

= 3.131  X 1025 atoms of Ar

(2) 52 u of He

The atomic mass of 1 He atom is 4 u. Therefore

4 u of He = 1 atom of He

1 u of He = (1 / 4) atoms of He

52 u of He = (52 / 4) atoms of He

= 13 atoms of He

(3) 52 g of He

The molar mass that is the mass of 6.022 X 1023 atoms of helium is 4g.

Hence 1 mole of He = 4 g of He = 6.022 X 1023 atoms of  He

1 g of He = (6.022 X 1023) / 4 atoms of  He

52 g of He = (6.022 X 1023X 52 ) / 4 atoms of  He

= 7.829 X 1024 atoms of He

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1st - 52 moles of argon

1mole of argon =6.022*1023

therefore,

atoms in 52 mole of argon = 6.022 * 1023 * 52

=313.144*1023

2nd - 52u of he

1 atom of he =4g

therefore,    1gm of he =1/4 atoms

number of atom present in 52 u(u can be taken as gm ) of he = 1/4 *52

=13 atoms

3rd - 52 d of he whats 52 d if its 52 g

then

4gm of he =6.022*1023

therefore, 1gm of he =(6.022*1023)/4

so              52 gm of he =(6.022*1023/4)*52

=7.8286*1024

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