Question

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution?

Answer 1

Answer:

Molarity = 0.01 M

Explanation:

Molarity is used to measure the concentration of a solution. It will be same for the whole solution or a small amount of solution if the solution is homogeneous.

So, Molarity of 200 mL of solution = Molarity of 50 mL of solution

$\mathbf{Molarity = \frac{number \ of \ moles \ of \ solute}{Volume \ of \ solution \ (in \ liters)}}$

$\mathbf{Moles = \frac{given \ mass \ of \ compound}{molar \ mass \ of \ compound}}$

given mass of aspirin = 360 mg = 0.36 g

molar mass of aspirin = 180 g

Volume of solution = 200 mL = 0.2 L

$\mathrm{Mole \ of \ Aspirin = \frac{0.36}{180} = \mathbf{0.002 \ moles}}$

$\mathrm{Molarity = \frac{0.002}{0.2} = \mathbf{0.01 \ M}}$

Therefore, Molarity = 0.01 M