The osmotic pressure of a 0.82 M HCl solution is 35.9 atm at 18°C. The van't Hoff factor for HCl at this concentration is
A) 1.8.
B) 17.2.
C) 1.5.
D) 2.00.

Question

Quizplus · Accepted Answer

The van't Hoff factor (i) can be calculated using the formula for osmotic pressure: $\pi = iMRT$, where $\pi$ is the osmotic pressure, $M$ is the molarity, $R$ is the gas constant (0.0821 L·atm/K·mol), and $T$ is the temperature in Kelvin. Rearranging the formula to solve for $i$ gives $i = \frac{\pi}{MRT}$. Substituting the given values ($\pi = 35.9$ atm, $M = 0.82$ M, $T = 18°C = 291K$), we find $i \approx 1.8$, indicating that HCl dissociates into two ions in solution, but not completely due to ion pairing or other interactions at this concentration.

The Osmotic Pressure of a 0