What is the molality of a #56*g# mass of common salt dissolved in #18*mL# of water?
Let's assume we have 1 mole of NaCl and 1 mole of 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!