Question

What is the molality of a `56*g` mass of common salt dissolved in `18*mL` of water?

Answer 1

`"Molality"` `=` `"Moles of solute"/"Kilograms of solvent"` `=` `"A somewhat"/" large value"`

Explanation:

`"Molality"` `=` `(1*mol)/(0.018*kg)` `=` `55.6*mol*kg^-1`.

I do not believe that a concentration this strong is physically realistic.

Answer 2

5.56 m

Explanation:

Let's assume we have 1 mole of NaCl and 1 mole of water.

Molality is calculated by dividing the moles of solute (NaCl) by the volume in L of the solvent (water)

The trick here is to figure out how much water you have.

The molar mass of water is 18g/mol.
Since the density of water is 1g/mL, 1 mole of water would have a volume of 18mL or 0.18L.

So molality of this would be

Molality = 1 mole NaCl / 0.18L water

5.56 m NaCl

Here is another lesson about calculating molality.

Hope this helps!