# 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:

$\overline{){\mathbf{\Pi }}{\mathbf{=}}{\mathbf{iMRT}}}$

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

97% (424 ratings)
###### 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.