Chemistry, asked by SHEGINSAVIOCS, 8 months ago

The molality of 5 molar urea solution having density 1.2 g/ml is
A
5 M
B
6.25 M
С
4.45 M
D
5.55 M​

Answers

Answered by cbd709963
6

Answer:

I think d 5.55

please mark me as drileant

Answered by probrainsme101
4

Answer:

The correct option is D. 5.55 M.

Concept:

Relation between molarity and molality is given by,

\frac{Molarity}{Molality}  = \frac{Mass \hspace{1mm}of  \hspace{1mm}solvent}{Volume \hspace{1mm} of  \hspace{1mm}solvent} \\     --------- (i)

Given:

Molarity of solution, M = 5 molar

M = 5 moles/1 L = 5 moles/1000 mL i.e., 5 moles are dissolved in 1000 mL of solvent.

Volume of solvent, V_{solv} = 1000 mL

As we know, Number of moles, n = \frac{Mass  \hspace{1mm}of  \hspace{1mm}solute}{Molecular \hspace{1mm} mass \hspace{1mm} of  \hspace{1mm}urea}

Molecular mass of urea, M = 60 g/mol

Hence, Mass of solute, m = n x M = 5 x 60 = 300 g

Density, d = 1.2 g/mL

According to the formula of density we have,

Density = \frac{Mass  \hspace{1mm}of \hspace{1mm}solute+mass \hspace{1mm}of \hspace{1mm}solvent}{Volume  \hspace{1mm}of  \hspace{1mm}solvent}

Density, d = \frac{m+m_{solv}}{V_{solv}}

m_{solv} = (d\times V_{solv})-m

         = (1.2\times 1000)-300

         = 1200-300

m_{solv} = 900 g

Now, using equation (i) we have,

\frac{Molarity}{Molality}  = \frac{m_{solv}}{V_{solv}}

\frac{5}{Molality}  = \frac{900 g}{1000 mL} = \frac{0.9 kg}{1 L} \\\frac{5}{Molality}  = 0.9\\Molality = \frac{5}{0.9} \\Molality = 5.55\hspace{1mm} molal

Hence, the molality of the solution is 5.55 molal.

#SPJ3

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