Question

10 litre solution of urea contains 240g urea. The active mass of urea will be

Answer 1

molar mass CO(NH2)2 = 60g/mol 
240g = 240/60 = 4 mol 
4mol dissolved in 10L = 4/10 = 0.4 mol /litre 

Active mass = 0.4mol /litre

Answer 2

Answer : The active mass of urea will be, 0.4 mole/L

Explanation : Given,

Mass of urea = 240 g

Molar mass of urea = 60 g/mole

Volume of solution = 10 L

Active mass : Active mass of the solution means molarity. The means the concentration of a substance expressed in moles per liter.

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

Formula used :

$\text{Active mass}=\text{Molarity}=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{volume of solution in liter}}$

Now put all the given values in this formula, we get the active mass of urea.

$\text{Active mass}=\text{Molarity}=\frac{240g}{60g/mole\times 10L}=0.4mole/L$

Therefore, the active mass of urea will be, 0.4 mole/L