Question

Which out of 100 g of sodium & 100 g of iron has more number of atoms & why?

[Atomic masses are : Na = 23 u, Fe = 56 u]

Explain with complete calculations & justifications.

Answer 1

atoms in 23 g of sodium= 6.023 x 10^23
atoms in 100g of sodium
= (6.023 x 10^23 x 100/23)
= 0.261 x 10 ^25

atoms in 56 g of iron= 6.023 x 10^23
atoms in 100 g of iron
=(6.023 x 10^23 x 100/ 56)
=0.107 x 10^25

we observe that 100g of sodium has more number of atoms than 100g of iron

Answer 2

no of mole of sodium =given weight of sodium/molecular weight of sodium
=100/23

no of arom in 100g Na =mole x Avogadro's constant
=100/23 x 6.023 x 10^23
again,
no of mole of Fe =given wt of Fe /mol wt of Fe
=100/56

so,
no of atom in 100g , Fe =mole of Fe x Avogadro's constant
=100/56 x 6.023 x 10^23

now you can see ,
no of atoms in 100g , Na > no of atoms in 100g , Fe