Chemistry | MHT CET 2018 | Discussion Page

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

$dm^{-3}$

Option B

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

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

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