The density of 3 molal solution of NaOH is 1.110g `mL^(-1)`. Calculate the molarity of the solution.

Options

A. 2M
B. 3.5M
C. 1.5M
D. 3M

Answer

D

Explanation

3 molal solution of `NaOH` means that 3 mole of `NaOH` are dissolved in 1000g of solvent.
`:.` Mass of solution = Mass of solvent `+` Mass of solute
`=1000g + (3 xx 40g) = 1120g`
Volume of solution `=(1120)/(1.110) mL = 1009.00mL`
(Since density of solution `= 1.110 gmL^(-1))`
Since 1009 mL solution contains 3 moles of `NaOH`
`:.` Molarity `=("Number of moles of solute")/("Volume of solution in litre")`
`=(3 mol)/(1009.00) xx 1000 = 2.97 M ~~ 3M`