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}=(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* 1000}{\text{Molar mass of }C_2H_5OH* \text{Volume of solution (in mL)}}`

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

`\text{Molarity}=(45.0g* 1000)/(46.07g/mole* 114.5mL)=8.53mole/L=8.53M`

Therefore, the concentration of solution is, 8.53 M.