Question

Calculate the mass percentage of aspirin $({{C}_{9}}{{H}_{8}}{{O}_{4}})$in acetonitrile $(C{{H}_{3}}CN)$ when 6.5 g of ${{C}_{9}}{{H}_{8}}{{O}_{4}}$is dissolved in 450 g of$C{{H}_{3}}CN$.

Answer 1

Hint: The amount of substance in lesser quantity is the solute, which is added into a large quantity of substance, called solvent. Together they make the components of a solution.

Formula used: mass percent of solute = $\dfrac{mass\,of\,solute}{mass\,of\,solution}\times 100$

Complete answer: We have been given aspirin, ${{C}_{9}}{{H}_{8}}{{O}_{4}}$, with the amount of 6.5 g. This is dissolved in acetonitrile, $C{{H}_{3}}CN$, whose amount is 450 g. We have to calculate the mass percentage of aspirin.
This is calculated by dividing the mass of aspirin by the total mass of solution, which is mass of aspirin + mass of acetonitrile, and then multiplying it by 100. So, this is calculated as,
Mass percent of aspirin = $\dfrac{mass\,of\,aspirin}{mass\,of\,aspirin+mass\,of\,acetonitrile}\times 100$
Mass percent of aspirin =$\dfrac{6.5\,g}{6.5\,g+450\,g}\times $ 100
Mass percent of aspirin = $\dfrac{6.5\,g}{456.5\,g}\times $100
Mass percent of aspirin = 0.0142$\times $100
Mass percent of aspirin = 1.42 %
Hence, mass percentage of 6.5 g of aspirin in 450 g of acetonitrile, is calculated to be 1.42 %.

Additional information: Aspirin is the common name for acetyl salicylic acid. It is prepared by the reaction of ethanoic anhydride and salicylic acid. It is commonly used as a medicine.

Note: Mass percent is asked here, so masses are divided and multiplied by 100. When the concentration is asked in moles, then molarity is used, which is the amount of solute in gram, per liter of solution (in L).