Question

Paracetamol is a medicine used to treat pain and fever. Its molecular formula is${\mathrm{C}}_8{\mathrm{H}}_9{\mathrm{NO}}_2$ calculate the number of C,N, and O atoms in a 500 mg paracetamol tablet

Answer 1

Paracetamol

• This medicine is used as both an analgesic and antipyretic.
• The molecular formula is ${\mathrm{C}}_8{\mathrm{H}}_9{\mathrm{NO}}_2$
• The molecular mass of paracetamol = 8 x mass of C + 9 x mass of H + 1 x mass of N + 2 x mass of O
• = 8 x 12 + 9 x 1 + 1 x 14 + 2 x 16
• = 151 g
• One mole contains 151 g of paracetamol.
• The number of moles in 500mg can be calculated as:

$$\begin{gathered} \mathrm{No}.\mathrm{of}\mathrm{moles}=\frac{\mathrm{Given}\mathrm{mass}}{\mathrm{gram}\mathrm{molecular}\mathrm{mass}}=\frac{500}{151}=3.3\mathrm{moles} \\ \mathrm{No}.\mathrm{of}\mathrm{atoms}=3.3\mathrm{x}6.022\mathrm{x}{10}^{23} \\ =19.87\mathrm{x}{10}^{23}\mathrm{atoms} \end{gathered}$$

In 1 mole, we have 8 carbon atoms, 9 hydrogen atoms, 1 nitrogen atom and 2 oxygen atoms

So in 3.3 moles,

• Number of C atoms = 3.3 x 8 = 26.4
• Number of H atoms = 3.3 x 9 = 29.7
• Number of N atoms = 3.3 x 1= 3.3
• Number of O atoms = 3.3 x 2 = 6.6