Acetylsalicylic acid (C9H8O4) is a monoprotic acid commonly known as aspirin. A typical aspirin tablet, however, contains only a small amount of the acid. In an experiment to determine its composition, an aspirin tablet was crushed and dissolved in water. It took 14.40 mL of 0.1466 M NaOH to neutralize the solution. Calculate the number of grains of aspirin in the tablet. (One grain = 0.0648 g and the molar mass of aspirin = 180.2 g/mol.)

6 grains

Explanation:

The equation of the reaction between NaOH and aspirin is;

C9H8O4(aq) + NaOH (aq) >C9H7O4Na(aq) + H2O(l)

Amount of NaOH reacted = concentration × volume = 0.1466 M × 14.40/1000 L = 2.11 × 10^-3 moles

Given that aspirin and NaOH react in a mole ratio of 1:1 from the balanced reaction equation above, the number of moles of aspirin reacted is 2.11 × 10^-3 moles

Hence mass of aspirin reacted = 2.11 × 10^-3 moles × 180.2 g/mol = 0.38 g

If 1 grain = 0.0648 g

x grains = 0.38 g

x= 0.38 g/0.0648 g

x= 6 grains