Discussion Forum



1)

 The molarity of urea (molar mass 60g  mol-1) solution by dissolving 15 g of urea in 500 cm3 of water is


A) 2 mol $dm^{-3}$

B) 0.5 mol $dm^{-3}$

C) 0.125 mol $dm^{-3}$

D) 0.0005 mol $dm^{-3}$

Answer:

Option B

Explanation:

Given, mass of urea =15 g

 Molar mass of urea = 60 g mol-1

 Volume = 500 cm3= 500 mL=0.5 L                 $\begin{bmatrix}\because 1 cm^{3} & =1mL \\1L & =1000mL \end{bmatrix}$

 $\therefore$  Molarity=

                Mass of solute in grams (w) / Molar mass of solute(M) x volume of solutionV(L)

 Molarity of urea= $\frac{15 g}{60g mol^{-1}\times0.5 L}$

  $\Rightarrow 0.5 mol/L=0.5 mol/dm^{2}$     $ (\because 1L=1dm^{2})$