Question

Calculate the molality of kcl solution prepared by dissolving 7.45g of kcl to make 500ml of the solution.density of solution=1.2g/ml

Answer 1

Hence the molarity will be 0.16m

Answer 2

Answer : The molality of KCl solution is 0.169 mole/Kg.

Solution : Given,

Mass of KCl = 7.45 g

Volume of solution = 500 ml

Density of solution = 1.2 g/ml

Molar mass of KCl = 74.5 g/mole

First we have to calculate the mass of solvent.

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

Now put the values in this formula, we get

$1.2g/ml=\frac{\text{ Mass of solution}}{500ml}$

By rearranging the terms, we get

Mass of solution = 600 g

As we know,  Mass of solution = Mass of solute + Mass of solvent

Mass of solvent = 600 - 7.45 = 592.55 g

Now we have to calculate the molality of KCl solution.

Formula used :

$Molality=\frac{\text{ Mass of solute}\times 1000}{\text{ Molar mass of solute}\times \text{ Mass of solvent in Kg}}$

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

$Molality=\frac{7.45g\times 1000}{74.5g/mole\times 592.55Kg}=0.169mole/Kg$

Therefore, the molality of KCl solution is 0.169 mole/Kg.