Find the molarity of the 5 molal urea solutio | vedclass

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Question

(B) Given: Molality $(m) = 5 \ mol / kg$,Density $(d) = 1.3 \ g / mL$,Molar mass of urea $(M_w) = 60.06 \ g / mol$. $5$ molal solution means $5$ moles

Vedclass · Accepted Answer

$= 5 \ M$

Vedclass · Answer

(B) Given: Molality $(m) = 5 \ mol / kg$,Density $(d) = 1.3 \ g / mL$,Molar mass of urea $(M_w) = 60.06 \ g / mol$. $5$ molal solution means $5$ moles of urea are present in $1000 \ g$ of solvent (water). Mass of urea = $5 \ mol 	imes 60.06 \ g / mol = 300.3 \ g$. Total mass of solution = Mass of solute + Mass of solvent = $300.3 \ g + 1000 \ g = 1300.3 \ g$. Volume of solution = $\frac{	ext{Mass}}{	ext{Density}} = \frac{1300.3 \ g}{1.3 \ g / mL} \approx 1000.23 \ mL = 1.00023 \ L$. Molarity $(M) = \frac{	ext{Moles of solute}}{	ext{Volume of solution in } L} = \frac{5 \ mol}{1.00023 \ L} \approx 4.9988 \ M$. Since $4.9988 \ M$ is approximately $5 \ M$,the correct option is $(B)$.

Find the molarity of the $5$ molal urea solution,whose density is $1.3 \ g / mL$ (given,molecular weight of urea is $60.06 \ g / mol$).

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