Question

A cough syrup contains 5.0 % ethyl alcohol C2H5Oh by mass. If the density of the solution is 0.9928 g/ml. Determine the molarity of the alcohol in the cough syrup.

Answer 1

Answer: The molarity of ethyl alcohol in cough syrup is 1.08 M

Explanation:

We are given:

(m/m) of ethyl alcohol = 5.0 %

This means that 5 g of ethyl alcohol is present in 100 g of solution.

To calculate volume of solution, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of solution = 0.9928 g/mL

Mass of solution = 100 g

Putting values in above equation, we get:

$0.9928g/mL=\frac{100g}{\text{Volume of solution}}\\\\\text{Volume of solution}=100.725mL$

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

We are given:

Mass of solute (ethyl alcohol) = 5 g

Molar mass of ethyl alcohol = 46.07 g/mol

Volume of solution = 100.725 mL

Putting values in above equation, we get:

$\text{Molarity of solution}=\frac{5g\times 1000}{46.07g/mol\times 100.725mL}\\\\\text{Molarity of solution}=1.08M$

Hence, the molarity of ethyl alcohol in cough syrup is 1.08 M