Question

Calculate the molality of a solution that contains 51.2 g of naphthalene, C10H8, in 500 mL of carbon tetrachloride. The density of CCl4 is 1.60 g/mL.

Answer 1

Answer: The molality of naphthalene solution is 0.499 m

Step-by-step explanation:

Density is defined as the ratio of mass and volume of a substance.

`\text{Density}=\frac{\text{Mass}}{\text{Volume}}` ......(1)

Given values:

Volume of carbon tetrachloride = 500 mL

Density of carbon tetrachloride = 1.60 g/mL

Putting values in equation 1, we get:

`\text{Mass of carbon tetrachloride}=(1.60g/mL* 500mL)=800g`

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:

`\text{Molality of solution}=\frac{\text{Given mass of solute}* 1000}{\text{Molar mass of solute}* \text{Mass of solvent (in g)}}` .....(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:

`\text{Molality of naphthalene}=(51.2* 1000)/(128.17* 800)\\\\\text{Molality of naphthalene}=0.499m`

Hence, the molality of naphthalene solution is 0.499 m