Question

The density of a 45.0 mass % solution of ethanol (C2H5OH) in water is 0.873 g/mL. What is the molarity of the solution?

Answer 1

Answer : The concentration of solution is, 8.53 M.

Explanation :

As we are given, 45.0 mass % solution of ethanol in water that means 45.0 g of ethanol present in 100 g of solution.

First we have to calculate the volume of solution.

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

$\text{Volume of solution}=\frac{100g}{0.873g/mL}=114.5mL$

Now we have to calculate the molarity of solution.

Mass of $C_2H_5OH$ = 45.0 g

Volume of solution = 114.5 mL

Molar mass of $C_2H_5OH$ = 46.07 g/mole

Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.

Formula used :

$\text{Molarity}=\frac{\text{Mass of }C_2H_5OH\times 1000}{\text{Molar mass of }C_2H_5OH\times \text{Volume of solution (in mL)}}$

Now put all the given values in this formula, we get:

$\text{Molarity}=\frac{45.0g\times 1000}{46.07g/mole\times 114.5mL}=8.53mole/L=8.53M$

Therefore, the concentration of solution is, 8.53 M.