Question

A drug contains 70% as many carbon atoms as hydrogen atoms and 14 times as many hydrogen atoms as oxygen atoms. In 1 gram 0.00318 moles of drug are present. Find the molecular formula.

Answer 1

Dear Student,

1) As there are mass as well as moles of drugs is given, we can calculate its molar mass = 1 / 0.00318 = 314.46 g mol^-1

2) Now, let us assume the number of oxygen atoms be = x

then according to the question the number of hydrogen atoms = 14x

​and the number of carbon atoms = 70 % of 14x = 9.8x ~ 10x

​Molecular formula = C_10xH_14xO_x

​the calculation for molar mass for the above molecular formula would be = 314.46 g mol^-1

===> $$\begin{gathered} \Rightarrow 12\times 10x+14x+16x=314.46 \\ \Rightarrow 150x=314.46 \\ \Rightarrow x=\frac{314.46}{150}=2.09 \\ x~2 \end{gathered}$$

Hence the molecular formula is C₂₀H₂₈O₂