Question

Dissolving `120g` of urea `(Mw = 60)` in `1000 g` of water gave a solution of density `1.15 g mL^(-1)`. The molarity of solution is:
A. `1.78 m`
B. `2.00 M`
C. `2.05 M`
D. `2.22 M`

Answer 1

Correct Answer - C
Molarity `= ("Moles of solute")/("Volume of solution(L)")`
Moles of urea `= (120)/(60) = 2`
Weight of solution = Weight of solvent + Weight of solute
`= 1000 + 120 = 1120 g`
`rArr "Volume" = (120 g)/(1.15g//mL) xx (1)/(1000mL//L) = 0.973 L`
`rArr "Molarity" = (2.000)/(0.973) = 2.05 M`