Question

If 0.2 g of nitrobenzene are added to 10.9 g of naphthalene, calculate the molality of the solution. (given: molar mass of nitrobenzene = 123.06 g/mole) report answers to one decimal place

Answer 1

To calculate the molality of a solution, we need to determine the number of moles of nitrobenzene and the mass of the solvent (naphthalene) in kilograms. Then, we can use the formula Molality = Moles of nitrobenzene / Mass of solvent in kg to calculate the molality. In this case, the molality of the solution is approximately 0.146 mol/kg.

Step-by-step explanation:

The molality of a solution is the amount of solute (in moles) per kilogram of solvent. To calculate the molality, we need to determine the number of moles of nitrobenzene and the mass of the solvent (naphthalene) in kilograms.

First, we need to convert the mass of nitrobenzene to moles:

Moles of nitrobenzene = 0.2 g / molar mass of nitrobenzene = 0.2 g / 123.06 g/mol = 0.0016 mol

The mass of the solvent (naphthalene) in kilograms = 10.9 g / 1000 = 0.0109 kg

Now, we can calculate the molality:

Molality of the solution = Moles of nitrobenzene / Mass of solvent in kg = 0.0016 mol / 0.0109 kg ≈ 0.146 mol/kg

Answer 2

Molality is defined as 1 mole of a solute in 1 kg of solvent.

Molality=

`(Number of moles of solute)/(Mass of solvent in kg)`

Number of moles of solute, n=

`(Given mass of the substance)/(Molar mass of the substance)`

Given mass of the nitrobenzene=0.2 g

Molar mass of the substance= 123.06 g mol⁻¹

Number of moles of nitrobenzene,

`n= (0.2 )/(123.06)`

Number of moles of nitrobenzene, n= 0.0016 mol

Mass of 10.9 g of naphthalene in kg=0.0109

`Molality= (0.0016)/(0.0109 )`

Molality= 0.146 m