molality of a solution?

Question

What is the molality of the solution prepared by mixing 160grams of NaOH and 16kilograms of H2O?

pls help me answer this....

Answer 1

molality = moles of solute/kilograms of solvent

naoh is your solute so u need to work out the amount of moles of naoh first.
moles = mass/molecular mass
moles = 160g/40g.mole
moles = 4
therefore molality = 4moles-1/16kg

Answer = molality = 0.25 mole.kg

i notice the others are answering molarity not molality

hope this helps

Answer 2

molarity is generally given in moles per litre.

How many litres are there in 16kg of water? (16)

What's the molar weight of NaOH? (22+16+1 = 37g)

How many moles of NaOH are there in 160g? (160/37)

You now have the number of moles, and the number of litres, so you can find out the molarity.

Also, when doing questions regarding moles, remember....number of mol es= conc. * vol

or...MOLES COPY VOLES

EDIT
I answered molarity, because in 6 years of chemistry, I'd never heard of molality. I thought it was just a typo. Sorry.

Answer 3

Molality (m) of this solution:

m = moles of solute / mass of solvent (in kg)

m = (160 g NaOH / 39.9971 g NaOH/mol) / 16 H2O

m = (4.00 mol NaOH) / 16 kg H2O

m = 2.5 x 10^(-1) mol NaOH/kg H2O

Answer 4

molality = 0.25 mole/kg
moles per kg

Answer 5

grams per L of solution equals molarity. so convert 16 kilograms to L the divide grams by that.