Question

find the no. of atoms in 20 g of SO3

Answer 1

Molecular mass of SO3 --- 32+3x16=80 Unified mass


Molar Mass=80gm

Given weight of SO3=20g
Number moles=given weight/gram molecular weight=20/80=1/4=0.25 moles

So 1 mole =80 gm of SO3 contains 6.023x 10²³ moelcules

0.25 moles[20g] conatins -----?
=6.023x10²³x0.25
=1.50x10²³ moleucles
Each moleucle of SO3 has 4 atoms.
so,Total number of atoms in SO3 is 4x1.50x10²³ 
=6x10²³ atoms

∴Total number of atoms in SO3 is 4x1.50x10²³ 
=6x10²³ atoms.