Question

the density of 2 molal aqueous solution of Naoh is 1.10gml . calculate molarity of the solution

Answer 1

2 molal aqueous solution means 2 moles of NaOH present in 1000g of solvent.
Volume= 1000×1.10 =1100
M= Given wt. ×1000/molecular wt. × wt. of solution
M=2×1000/40×1100
=1/22
= 0.045

Answer 2

Answer: Molarity of the solution is 2.04 M.

Explanation:

Molality of a solution is defined as the number of moles of solute dissolved per kg of the solvent.

$Molarity=\frac{n}{W_s}$

Given molality = 2m which means 2 moles of $NaOH$ is dissolved in 1 kg of solvent

where,

n = moles of solute  = 2

$W_s$ = mass of solvent in kg = 1 kg = 1000 g

mass of solute $NaOH=moles\times {\text {molar mass}}=2\times 40g/mol=80g$

Mass of solution = mass of solute + mass of solvent = 80 g+ 1000 g = 1080 g

Density of solution =$\frac{\text {mass of solution}}}{\text {Volume of solution}}$

$1.10g/ml=\frac{1080}{\text {Volume of solution}}$

${\text {Volume of solution}}=982ml$

Molarity of a solution is defined as the number of moles of solute dissolved per Liter of the solution.

$Molarity=\frac{n\times 1000}{V_s}$

where,

n= moles of solute  = 2

$V_s$ = volume of solution in ml = 982 ml

$Molarity=\frac{2moles\times 1000}{982ml}=2.04M$

Thus molarity of the solution is 2.04 M.