Question

If the density of 1 M NaOH solution is 2 g/cm3 then the molality of the solution is

Answer 1

Answer:

Explanation:

MOLALITY= MOLES OF SOLUTE ÷ MASS OF SOLUTION

density given is 2g/cm^3

therefore mass of NaOH is 2g

molar mass of NaOH is 40g

moles of NaOH = 2/40=0.05

mass of solution is 100g

therefore MOLALITY= (0.05/100) × 1000

                                 = 0.5 m

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Answer 2

The molality of the solution is 0.5 mol/kg

GIVEN

Molarity of NaOH solution = 1 M

Density of NaOH solution = 2g/cm³

TO FIND

Molality of the solution

SOLUTION

We can simply solve the above problem as follows;

We know that,

$molality = \frac{moles \: of \: solute}{mass \: of \: solvent \: in \: grams} \times 1000$

Molarity = 1 M

This means that, 1 mole of NaOH is present in 1 Litre of solution.

Density = mass of solution /volume of solution = 2g/cm³

we know that,

1 cm³ = 1 ml

So,

$2 = \frac{mass \: of \: solution}{1000 }$

$= 2000gm$

We know that,

Mass of solution = mass of solute + mass of solvent

2000 = 40 grams + mass of solvent

Mass of solvent = 2000-40 = 1960 grams

So,

$m = \frac{1}{1960} \times 1000$

m = 0.5 mol/kg

Hence, The molality of the solution is 0.5 mol/kg

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