Which of the following is $NOT$ used as a semipermeable membrane?

Osmotic pressure of a urea solution at $10\,^{\circ}C$ is $500\,mm$. The osmotic pressure of the solution becomes $105.3\,mm$ when it is diluted and the temperature is raised to $25\,^{\circ}C$. The extent of dilution is .......... times.

$A$ semipermeable membrane is that which permits the passage of:

Which of the following pairs of solutions is expected to be isotonic at the same temperature?

The osmotic pressures of $0.010 \ M$ solutions of $KI$ and of sucrose $(C_{12}H_{22}O_{11})$ are $0.432 \ atm$ and $0.24 \ atm$ respectively. The van't Hoff factor for $KI$ is

Which of the following would have the highest osmotic pressure? (Assume that all salts are $90\%$ dissociated.)