Question

15 grams of Urea is dissolved in 200 ml of a solution calculate the molarity if the density of the solution is 1.03 gram per ml calculate the molality.
(Urea =NH2-CO-NH2)
Hence molecular wt is 60

Answer 1

Answer:

1.25M

Explanation:

hope this help you

Answer 2

Answer:

The molarity, M, of the solution calculated is $1.25M$.

The molality, m, of the solution calculated is $1.30molal$.

Explanation:

Data given,

The weight of urea ( $CO(NH_{2})_{2}$ ) = $15g$

The volume of the solution = $200ml$ = $0.2L$

The density of the solution = $1.03g/ml$

The urea's molecular weight ( $CO(NH_{2})_{2}$ ) = $60g/mol$

The molarity of the solution, M =?

The molality of the solution, m =?

As we know,

• Molarity = $\frac{Number of moles ( solute )}{Volume of solution (L)}$       -------equation (1)

And,

• Molality = $\frac{Number of moles ( solute )}{weight of solvent (kg)}$       -------equation (2)

Firstly, we have to find out the number of moles of urea:

• Number of moles of urea = $\frac{Given weight}{Molar weight}$ = $\frac{15}{60}$ = $0.25mol$

Therefore,

• Molarity = $\frac{Number of moles ( solute )}{Volume of solution (L)}$ = $\frac{0.25}{0.2}$ = $1.25M$

Now we have to find out the weight of the solvent:

• The density of solution = $\frac{mass}{volume}$
• The weight of the solution = $1.03\times 200$ = $206g$

Thus, the weight of solvent = total weight - the weight of urea = $206-15$ = $191g$ = $0.191kg$

Therefore,

• Molality = $\frac{Number of moles ( solute )}{weight of solvent (kg)}$ = $\frac{0.25}{0.191}$ = $1.30molal$

Hence, molarity is $1.25M$ and molality is $1.30molal$.