<u>Answer:</u> The molality of naphthalene solution is 0.499 m
<u>Explanation:</u>
Density is defined as the ratio of mass and volume of a substance.
......(1)
Given values:
Volume of carbon tetrachloride = 500 mL
Density of carbon tetrachloride = 1.60 g/mL
Putting values in equation 1, we get:

Molality is defined as the amount of solute expressed in the number of moles present per kilogram of solvent. The units of molarity are mol/kg. The formula used to calculate molarity:
.....(2)
Given values:
Given mass of naphthalene = 51.2 g
Molar mass of naphthalene = 128.17 g/mol
Mass of solvent = 800 g
Putting values in equation 2, we get:

Hence, the molality of naphthalene solution is 0.499 m
Answer:
0.4383 g
Explanation:
Molality is defined as the moles of the solute present in 1 kg of the solvent.
It is represented by 'm'.
Thus,
Given that:
Mass of solvent, water = 150 g = 0.15 kg ( 1 g = 0.001 g )
Molality = 0.050 m
So,

Molar mass of NaCl = 58.44 g/mol
Mass = Moles*Molar mass =
= 0.4383 g
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