Question

Calculate The Mass Of Urea Required In Making 2.5 Kg Of 0.25 Molal Aqua Solution

Answer 1

Explanation:

With reference to aqua regia, choose the correct option(s)

A. The yellow colour of aqua regia is due to the presence of NOCl and Cl_

B. Aqua regia is prepared by mixing conc. HCl and conc. HNO_ in 3 : 1 (v/v) ratio

C. Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state

D. Reaction of gold with aqua regia produces NO_ in the absence of air

Answer 2

$\fbox{\texttt{\green{Answer\::}}}$

Mass of urea required = 37 g

$\fbox{\texttt{\pink{Given\::}}}$

Amount of aqueous solution = 2.5 kg of 0.25 m

$\fbox{\texttt{\orange{To\:find\::}}}$

The mass of urea required to make the solution.

$\fbox{\texttt{\red{How\:to\:Find\::}}}$

0.25 molal aqueous solution of urea means that :-

Moles of urea = 0.25 mole

Mass of solvent (water) = 1 kg = 1000 g

Molar mass of urea $\bold{(NH_2CONH_2)}$ :-

$\implies\bold{14+2+12+16+14+2}$

$\implies\bold{60\:g\:mol^{-1}}$

$\therefore\bold{0.25\:mole\:of\:urea=0 25\:mole\times{60\:g\:mol^{-1}}}$

$\implies\bold{15\:g}$

$\bold{Total\:mass\:of\:solution=1000+15\:g=1.015\:g}$

$\implies\bold{1.015\:kg}$

$\bold{Thus,\:1.015\:kg\:of\:solution\:contains\:urea=15\:g}$

$\therefore\bold{2.5\:kg\:of\:solution\:will\:require\:urea}$

$\implies\bold{\frac{15\:g}{1.015\:kg}\times{2.5\:kg}=37\:g.}$