Question

Calculate the following, present in $16gof{O}_2$.
(a) Number of moles.
(b) Number of molecules.

• A. a) 0.5, b) $3.0115\times {10}^{23}$
• B. a) 0.7, b) $4.678\times {10}^{23}$
• C. a) 0.5, b) $2.634\times {10}^{23}$
• D. a) 0.1, b) $3.0115\times {10}^{34}$

Answer 1

The correct option is A a) 0.5, b) $3.0115\times {10}^{23}$

$Massofoxygen=M_{O_2}=16g$
$Grammolecularweightofoxygen=GMWof{O}_2=32g$
$\left(a\right)Numberofmoles=n=?$
$weknow,n_{o_2}=\frac{m_{o_2}}{GMW{o}_2}........\left(1\right)$
$Substitutingtheabovevaluesfromthedatainequation\left(1\right),weget,$
$n_{o_2}=\frac{16}{32}=\frac{1}{2}=0.5$
$Therefore,thenumberofmolesofoxygenpresentin16gofoxygen=0.5$
$\left(b\right)Numberofmolecules=N_m=?$
$Weknow,$
$N_m=\frac{m}{GMW}\times 6.023\times {10}^{23}.....\left(1\right)$
$Substitutingthevaluesfromthedatainequation\left(1\right),weget,$
$N_m=\frac{16}{32}\times 6.023\times {10}^{23}$
$=3.0115\times {10}^{23}$