Question

If 15g of urea is dissolved in 330g of water. Find molarity of solution, if density of solution is 1.8 g/ml.​

Answer 1

Given that, 15g of urea is dissolved in 330g of water.

• Density of solution = 1.8 g/ml

First of all we have to calculate total volume of the solution.

A) Weight of the solution :

➝ W = W₁ + W₂

• W₁ denotes weight of urea
• W₂ denotes weight of water

➝ W = 15 + 330

➝ W = 345 g

B) Volume of the solution :

Formula of density is given by;

➝ d = W / V

Where V denotes volume of the solution.

➝ 1.8 = 345 / V

➝ V = 345/1.8

➝ V = 191.67 ml

C) Moles of urea in the solution :

➝ n = W₁ / Mw

• Mw denotes molar mass of urea which is 60 grams per mole

➝ n = 15 / 60

➝ n = 0.25

After finding moles of solute (urea) and volume of the solution we can calculate molarity of the solution.

$\sf:\implies\:Molarity=\dfrac{n\times 1000}{V_{ml}}$

$\sf:\implies\:Molarity=\dfrac{0.25\times 1000}{191.67}$

$\sf:\implies\:Molarity=\dfrac{250}{191.67}$

$:\implies\:\underline{\boxed{\bf{\red{Molarity=1.3\:molar}}}}$