Question

molality of pure water ???

Answer 1

At room temperature it's 55.55 M.



We can derive it in the following way,
Density = mass / volume = 1000kg/m^3

volume = (mass/1000) m^3

Let the no. of moles there be x,

Now,

volume = (18x / 1000)m^3.

since mass = (no. of moles × molar mass),

Molarity =( x/ (18x/1000)) M = (1000/18) M = 55.55 M

Answer 2

The molality of pure water:

Molality is a measure of the concentration of a solute in a solution in relation to the amount of substance in a definite amount of mass of the solvent.

The molality of pure water:

The density of water= 1g/ml

The molar mass of water=18

Moles of water in 1000g or 1kg= 1000/18=55.5

So, the molality is equal to 55.55.