Question

what is number of atoms in 4 gram of O2

Answer 1

32 gms of O2 contain 6.023×10^23 atoms
therefore 1 gm will contain 6.023×10^23/32
so 4 gms of O2 will contain 6.023×10^23×4/32=0.752×10^23 atoms

Answer 2

First we will calculate the number of moles(n).
given mass(m)= 4g
Molecular mass(M)= 2×16=32u
We know that,
n= m/M
n= 4/32= 1/8

we also know that
n= Number of atoms/Avogadro's constant
1/8= N/6.022×10²³
8N=6.022×10²³
N= 6.022×10²³/8=0.75275×10²³ atoms.
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