Question

If 11.2 g of naphthalene, C10H8, is dissolved in 107.8 g of chloroform, CHCl3, what is the molality of the solution?

a. 0.811m
b. 0.0941 m
c.12.4 m
d. 0.0875 m
e. 0.0969m

Answer 1

To determine the molality of a naphthalene solution in chloroform, calculate the moles of naphthalene, convert the mass of chloroform to kilograms, and divide the moles of solute by the mass of the solvent in kg to find a molality of approximately 0.811m. Therefore, the correct answer is (a) 0.811m.

Step-by-step explanation:

To calculate the molality of the solution, you need to know the number of moles of solute and the mass of solvent in kilograms. First, calculate the moles of naphthalene:

• Molecular weight of C10H8 = 128.17 g/mol
• Moles of naphthalene (C10H8) = 11.2 g / 128.17 g/mol

Next, convert the mass of the chloroform solvent to kilograms:

• 107.8 g CHCl3 = 0.1078 kg

Now, use the formula for molality:

• Molality (m) = Moles of solute / Mass of solvent in kilograms

Substitute the calculated values to get the molality of the solution:

• Molality (m) = (11.2 g / 128.17 g/mol) / 0.1078 kg
• Molality (m) ≈ 0.811 m

Therefore, the correct answer is (a) 0.811m.

Answer 2

Answer: 0.811m

Explanation: Molarity is the moles of solute present per kg of solvent.

Molar mass of C10H8 = . 128.17 g/mol

No. of moles = given mass/molar mass

11.2g C10H8 = 11.2/128.17 g/mol C10H8

= 0.0874 mol C10H8

NOW 107.8g solvent (chloroform) contains 0.0879 molecules (naphthalene)

1000g '' will contain (0.0879/107.8 x 1000) mole solute

= 0.811 mole

Molarity of the solution is 0.811 m (option A)