Question

10% w/w NaOH molality

Answer 1

Answer:

It is given that the concentration of the NaOH solution is 10% w/w.

This refers to the case wherein 10g of NaOH is mixed with 100g of solution.

Now lets assume that the given mass of NaOH is 10g.

Number of moles of NaOH = 10g / 40g = 0.25 moles

Also it is given that mass of solution is 100g

Therefore mass of solvent = Mass of solution - Mass of solute

→ Mass of solvent = 100g - 10g = 90g

→ Mass of solvent = 90g = 0.09 Kg

Molality formula = Number of moles of solute / Mass of solvent (in Kg)

⇒ Molality of given sample = 0.25 / 0.09

⇒ Molality of given sample = 2.78 m (approx.)

Hence the molality of 10% w/w NaOH solution is 2.78 m (approx.)