Question

How many molecules of aspirin (Molar mass = $180\text{g/mol}$) are present in $50\text{mg}$ of the tablet?

• A. $1.673\times {10}^{20}$
• B. $1.673\times {10}^{21}$
• C. $2.373\times {10}^{20}$
• D. $3.273\times {10}^{20}$

Answer 1

The correct option is A $1.673\times {10}^{20}$

Number of moles = $\frac{Givenmassingrams}{Molecularmass}$

Number of moles of aspirin $=\frac{50grams}{180}=0.27moles$

Now Number of molecules of aspirin =

$Numberofmolesofaspirin\times Avogadr{o}^{\prime }sNumber$

$=0.27\times 6.022\times {10}^{23}$

$=1.62\times {10}^{23}molecules$