Problem: A lithium salt used in lubricating grease has the formula LiCn H2n + 1 O2. The salt is soluble in water to the extent of 0.036 g per 100 g of water at 25 oC. The osmotic pressure of this solution is found to be 57.1 torr.Assuming that molality and molarity in such a dilute solution are the same and that the lithium salt is completely dissociated in the solution, determine an appropriate value of n in the formula for the salt.

FREE Expert Solution

We’re being asked to determine the solution with the highest osmotic pressure.


The osmotic pressure (Π) of a solution is related to the molarity of the solution:


Π=iMRT


where:

i = van’t Hoff factor

M = molarity of the solution (in M or mol/L)

R = gas constant (0.08206 atm • L/mol • K)

T = temperature


We will do the following steps to solve the problem:

Step 1: Determine van't Hoff factor

Step 2: Convert torr to atm

Step 3: Calculate the molarity using osmotic pressure

Step 4: Calculate the moles of solute

Step 5: Calculate the molar mass of the salt

Step 6: Determine n using the molar mass of the salt

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Problem Details

A lithium salt used in lubricating grease has the formula LiCn H2n + 1 O2. The salt is soluble in water to the extent of 0.036 g per 100 g of water at 25 oC. The osmotic pressure of this solution is found to be 57.1 torr.

Assuming that molality and molarity in such a dilute solution are the same and that the lithium salt is completely dissociated in the solution, determine an appropriate value of n in the formula for the salt.

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Our tutors have indicated that to solve this problem you will need to apply the The Colligative Properties concept. You can view video lessons to learn The Colligative Properties. Or if you need more The Colligative Properties practice, you can also practice The Colligative Properties practice problems.

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