Question

The plot of osmotic pressure II) vs concentration (mol L^–1 ) for a solution gives a straight line with slope 25.73 L bar mol^–1 . The temperature at which the osmotic pressure measurement is done is
(Use R = 0.083 L bar mol–1 K^–1 )

• A. 37°C
• B. 310°C
• C. 25.73°C
• D. 12.05°C

Answer 1

The Correct Option is A

A plot of osmotic pressure (Π) against concentration (mol L^-1) for a solution yields a linear relationship with a slope of 25.73 L bar mol^-1. The temperature of the osmotic pressure measurement is to be determined.

(R = 0.083 L bar mol^-1 K^-1)

Solution:

The van't Hoff equation for osmotic pressure is:

Π = CRT

where:

• Π represents osmotic pressure
• C is the molar concentration (mol L^-1)
• R is the ideal gas constant (0.083 L bar mol^-1 K^-1)
• T denotes the temperature in Kelvin

Rearranging the equation to highlight the linear relationship:

Π = (RT)C

This equation is in the form of y = mx, where:

• y corresponds to Π
• x corresponds to C
• m, the slope, is equal to RT

Given the slope (RT) = 25.73 L bar mol^-1 and R = 0.083 L bar mol^-1 K^-1, the temperature (T) can be calculated as:

T = slope / R

T = 25.73 / 0.083

T ≈ 310 K

To convert the temperature from Kelvin to Celsius:

T (°C) = T (K) - 273.15

T (°C) = 310 - 273.15

T (°C) ≈ 36.85°C

This is approximately 37°C.

Option 1: 37°C