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

0.07mol/kg

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 NaCl  =  

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

   Number of moles of NaCl  =   = 2.05mole

So;

  molality  =   = 0.07mol/kg

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.