Molality (W) is the ratio of the amount of substance of a solute (in moles – n) to the mass in kilograms of the solvent (m1). It can be calculated by the following formula:
W = n/m1
Step 1 - Let's discover how many moles of sodium fluoride is needed first.
Let's transform 600 g of water to kilograms:
1 g = 0.001 kg
600 g = 0.6 kg
W = 0.600m
m1 = 0.6
0.600 = n/0.6
n = 0.36 moles of sodium floride
Step 2 - Let's transform 0.36 moles of NaF into grams. Let's use the following formula: mass = moles x molar mass
molar mass of NaF = 42 g/mol
mass = 0.36 x 42
mass = 15.12 g
Answer: 15.12 g of NaF