Lysine is an amino acid that is an essential part of nutrition but which is not synthesized by the human body. What is the molar mass of lysine if 750.0 mL of a solution containing 8.60 g of lysine has an osmotic pressure of 1.918 atm? Temperature = 25.0°C
A)110. g/mol
B)146 g/mol
C)220. g/mol
D)1340 g/mol
E)1780 g/mol

Question

Quizplus · Accepted Answer

The molar mass of lysine can be calculated using the formula for osmotic pressure: $\pi = \frac{n}{V}RT$, where $\pi$ is the osmotic pressure, $n$ is the number of moles of solute, $V$ is the volume of the solution in liters, $R$ is the ideal gas constant (0.0821 L·atm/K·mol), and $T$ is the temperature in Kelvin. First, convert the temperature to Kelvin: $25.0°C + 273.15 = 298.15 K$. Then, rearrange the formula to solve for $n$: $n = \pi V / RT$. Substituting the given values: $n = (1.918 \, \text{atm} \times 0.750 \, \text{L}) / (0.0821 \, \text{L·atm/K·mol} \times 298.15 \, \text{K})$. This calculation gives the number of moles of lysine, which can then be used to find the molar mass: $M = \text{mass} / n$. Given the mass of lysine is 8.60 g, you can calculate the molar mass. The correct calculation leads to a molar mass close to 146 g/mol, making option B the correct answer.

Lysine Is an Amino Acid That Is an Essential Part