[tex]125gms[/tex] of oxygen gas contains [tex]2.35\times 10^{24}[/tex] molecules of oxygen.
The molecular weight of oxygen[tex]=16[/tex]
Therefore,[tex]O_2=2\times 16\\=32[/tex]
No.of Moles of oxygen in 125g is,
[tex]\frac{125}{32}=3.9 g[/tex]
1mole of oxygen contains [tex]6.023\times10^23 molecules[/tex]
No.of oxygen molecules in 3.9 g of oxygen is,
[tex]3.9 \times 6.023 \times10^23=2.348 \times 10^24[/tex]
Which can be roundoff and written as [tex]2.35 \times10^{24}[/tex]
Therefore, 125gms of oxygen gas contains [tex]2.35 \times10^{24}[/tex] molecules of oxygen.
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