Question

A 376 mg sample of a nonelectrolyte compound isolated from throat lozenges was dissolved in water to produce 10.0 mL of a solution at 25°C. The osmotic pressure of this solution was measured and found to be 4.89 atm. What is the molar mass of this compound?

A. 489 g/mol
B. 941 g/mol
C. 48.9 g/mol
D. 199 g/mol
E. 188 g/mol

Answer 1

A. 489 g/mol. To find the molar mass of the nonelectrolyte compound, one must first calculate the molarity using the osmotic pressure, temperature, and volume,

Step-by-step explanation:

The student's question asks for the calculation of the molar mass of a nonelectrolyte compound using osmotic pressure data. The osmotic pressure (Π) can be calculated using the formula Π = iMRT, where i is the van't Hoff factor (in this case, 1 for a nonelectrolyte), M is the molarity, R is the ideal gas constant (0.0821 L·atm/K·mol), and T is the temperature in Kelvin. Here we are given Π = 4.89 atm, the volume V = 10.0 mL (0.010 L), and the temperature T = 25°C (298 K).then use the molarity to find the moles, and finally divide the mass of the compound by the number of moles.

To find M, the molarity, we rearrange the equation to M = Π / (RT), then we can calculate the moles of solute (n) and use the mass of the solute (m = 376 mg or 0.376 g) to find the molar mass (Molar mass = m/n). Using these steps, the molar mass will be found, and we can match it with the correct answer option provided.

To answer the question: To calculate the molar mass of the compound, we find the molarity first, which is M = 4.89 atm / (0.0821 L·atm/(K·mol) × 298 K), and then use that to calculate the molar mass from the grams of the compound provided.