Question

What's the molality of a solution with 120 g of NaCl and 30 kg of water?

Answer 1

0.068

Step-by-step explanation:

Answer 2

0.07mol/kg

Step-by-step explanation:

Given parameters:

Mass of NaCl solution = 120g

Mass of water = 30kg

Unknown:

Molality of the solution =?

Solution:

The molality of a solution is the number of moles of the solute per mass of the solution.

Molality =
`(number of moles of solute)/(mass of solution)`

Number of moles of NaCl =
`(mass)/(molar mass)`

Molar mass of NaCl = 23 + 35.5 = 58.5g/mol

Number of moles of NaCl =
`(120)/(58.5)` = 2.05mole

So;

molality =
`(2.05)/(30)` = 0.07mol/kg