The freezing point of benzene is 5.5°C. What is the freezing point of a solution of 8.50 g of naphthalene (C10H8) in 425 g of benzene (Kf of benzene = 4.90°C/m)?

delta T = Kf m
m = mols/kg solvent.
Change 8.5 g naphthalene to mols and 425 g benzene to kg.
That will get delta T. Then
5.5 - delta T will give the new f.p.
Post your work if you get stuck or if you wish to check your answer.

A 1.60 g sample of napthalene (a non-electrolyte with a formula of C10H8) is dissolved in 20.0 g of benzene (C6H6). The freezing point of benzene is 5.5°C and Kf = 5.12 kg/mol. What is the freezing point of the solution?

What is freezing point depression when 125g of br2 is added to 755g of Benzene? Kf(benzen e = 5.12°C\m.

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To find the freezing point of the solution, we can use the formula:

delta T = Kf * m

Where:
- delta T is the change in freezing point
- Kf is the freezing point depression constant (constant for a particular solvent)
- m is the molality of the solute (mols/kg solvent)

Now let's solve the problem step by step:

Step 1: Convert grams to moles
We have 8.50 g of naphthalene. To convert it to moles, we need to divide by the molar mass of naphthalene (C10H8) which is 128.17 g/mol.
moles of naphthalene = 8.50 g / 128.17 g/mol = 0.0663 mol

Step 2: Convert grams to kilograms
We have 425 g of benzene. To convert it to kilograms, we divide by 1000.
mass of benzene = 425 g / 1000 = 0.425 kg

Step 3: Calculate molality
Molality (m) is defined as moles of solute divided by kilograms of solvent.
mols/kg solvent = 0.0663 mol / 0.425 kg = 0.1558 m

Step 4: Calculate delta T
Using the given Kf value for benzene (4.90°C/m), we can substitute the values into the formula:
delta T = 4.90°C/m * 0.1558 m = 0.762°C

Step 5: Calculate the new freezing point
To find the new freezing point, we subtract delta T from the freezing point of pure benzene.
new freezing point = 5.5°C - 0.762°C = 4.738°C

Therefore, the freezing point of the solution of 8.50 g of naphthalene in 425 g of benzene is approximately 4.738°C.