Question

In a laboratory experiment, a student found that a 144-mL aqueous solution containing 2.512 g of a compound had an osmotic pressure of 13.8 mmHg at 298 K. The compound was also found to be nonvolatile and a nonelectrolyte. What is the molar mass of this compound?g/mol

Answer 1

Step-by-step explanation:

Information provided:

Volume solution = V = 144 mL

Weight of compound = Wc = 2.512 g

Osmotic pressure = π = 13.8 mmHg

T = absolute temperature = 298 K

R = 0.082 atm L/mol K

M = molar mass = unknown

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Procedure:

1 atm = 760 mmHg => π = 13.8 mmHg x (1 atm/760 mm Hg) = 0.018 atm

1 L = 1000 mL => V = 144 mL x (1 L/1000 mL) = 0.144 L

π is calculated as follows:

π = C x R x T

C = Wc/(M x V)

So:

`\begin{gathered} \pi\text{ = }\frac{Wc}{M\text{ x V}}\text{ x R x T} \\ M\text{ = }\frac{Wc}{\pi\text{ x V}}\text{ x R x T} \\ M\text{ = }\frac{2.512\text{ g}}{0.018\text{ atm x 0.144 L}}x\text{ 0.082 }\frac{atm\text{ L}}{mol\text{ K}}\text{ x 298 K} \\ M\text{ = 23681.8 g/mol} \end{gathered}`

(The result is somewhat high according to the values of the parameters)

Answer: M = 23681.8 g/mol