Question

How many oxygen atoms are present in a tablet weighing \[360mg\] of Aspirin (Aspirin-\[{C_9}{H_8}{O_4}\]).

Answer 1

Hint:Aspirin is an anti-inflammatory drug used for relieving pain, inflammation and fever. The number of oxygen atoms can be determined using the mole concept.

Complete step by step answer:Aspirin is an organic compound also known as acetylsalicylic acid. The molecular formula of aspirin is \[{C_9}{H_8}{O_4}\]. It is an aromatic compound containing a benzene ring. The functional groups attached to the benzene ring are one carboxylic (\[COOH\]) group and one acetyl (\[COC{H_3}\]) group. The structure of aspirin is

The molecular or chemical formula of Aspirin is \[{C_9}{H_8}{O_4}\]. The molecular weight of Aspirin is =
\[9\] x atomic mass of \[C\] atom + \[8\] x atomic mass of \[H\] atom + \[4\] x atomic mass of \[O\] atom
=$9 \times 12 + 8 \times 1 + 4 \times 16 = 180g$
A tablet of Aspirin weighs \[360mg\]. Thus the moles of Aspirin contain in \[360mg\] of Aspirin is,
$moles = \dfrac{{weight}}{{molar{\text{ }}mass}}$
$ = \dfrac{{360 \times {{10}^{ - 3}}}}{{180}} = 2 \times {10^{ - 3}}$
One molecule of Aspirin contains four molecules of oxygen atom. Thus the moles of oxygen in \[2{\text{ }} \times {10^{ - 3}}\] moles of Aspirin = $4 \times 2 \times {10^{ - 3}} = 8 \times {10^{ - 3}}$
According to Avogadro’s law, one gram mole of a substance contains \[6.023 \times {10^{23}}\] atoms. Here the number of moles of oxygen is \[8 \times {10^{ - 3}}\]. Therefore the number of oxygen atoms present in \[8{\text{ }} \times {10^{ - 3}}\] moles of oxygen = moles of oxygen x Avogadro’s number
= $8 \times {10^{ - 3}} \times 6.023 \times {10^{23}} = 4.81 \times {10^{21}}$
Hence \[4.81 \times {10^{21}}\] number of oxygen atoms is present in a tablet weighing \[360mg\] of Aspirin (Aspirin-\[{C_9}{H_8}{O_4}\]).

Note:Before the discovery of aspirin, \[2\] -hydroxy benzoic acid was used as a drug. This leads to severe irritation in the stomach after consumption. In order to avoid such irritation the hydroxyl group was protected with acetyl group.