Question

what is the molality of 21% of HNO3 solution​

Answer 1

hi Dear

21 % means 100 g of solution has 21 g of HNO3 and 79 g of H2O

• Not of moles of HNO3 = 21/63= 1/3
• mass of solvent = 0.071

Molarity =0.071/3 =0.0237

hope you understood

Answer 2

Answer : The molality is, 4.22 mole/Kg

Solution :

As we are given 21% of $HNO_3$ solution​ that means 21 grams of $HNO_3$ present in 100 grams of solution.

Mass of $HNO_3$ = 21 g

Mass of solution = 100 g

First we have to calculate the mass of water.

Mass of water = 100 - 21 = 79 g

Molality : It us defined as the number of moles of solute present in one kilogram of solvent.

Now we have to calculate the molality of solution.

Formula used :

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

In this question, solute is $HNO_3$ and solvent is water.

Molar mass of $HNO_3$ = 63 g/mole

Now put all the given values in the above formula, we get the molality.

$Molality=\frac{21g\times 1000}{63g/mole\times 79g}=4.22mole/Kg$

Therefore, the molality is, 4.22 mole/Kg