Q.93 Chemistry · Section B ⭐ 360° Option Elimination Active

NEET 2024 Chemistry Question 93 Solution

Topic: Solutions · Official NTA Booklet Code T1

Question

The plot of osmotic pressure (Π) 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)

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Verified Against NTA Final Answer Key

Option (3) : 37°C

📚 Solutions Easy

📋 Given Parameters & Problem Setup

Graph Plot of osmotic pressure (Π) vs concentration (C in mol L^-1)

Slope of straight line 25.73 L bar mol^-1

Universal gas constant (R) 0.083 L bar mol^-1 K^-1

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The 30-Second Exam Hall Shortcut: ⚡ Kelvin to Celsius Temperature Trap

⏱️ Save ~30 seconds

Π = C · R · T -> Slope = R · T -> T = Slope / R = 25.73 / 0.083 = 310 K! Convert to Celsius: 310 - 273 = 37°C! Don’t pick 310°C (Option 4 trap)!

1 Van ’t Hoff equation for osmotic pressure: Π = C R T.

2 Comparing with y = mx: y = Π, x = C, Slope m = R T.

3 Solve for absolute temperature: T = Slope / R = 25.73 / 0.083 = 310 K.

4 Convert absolute temperature T in Kelvin to Celsius: t(°C) = 310 - 273 = 37°C.

5 Option (4) gives 310°C as a trap; the correct Celsius answer is 37°C.

6 Option (3) in 10 seconds!

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Why You Can 100% Trust This Shortcut: NCERT Chemistry · Solutions (Colligative properties: Van ’t Hoff equation for osmotic pressure Π = CRT).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Van ’t Hoff Equation for Osmotic Pressure

For a dilute solution of a non-electrolyte, the osmotic pressure Π is directly proportional to the molar concentration C and absolute temperature T:

\Pi = C R T

Step 2

Identification of Graphical Slope

Plotting Π on the y-axis against concentration C on the x-axis gives a straight line passing through the origin: y = mx ⟹ Π = (RT) · C. Therefore, the slope of the line equals the product of the gas constant R and absolute temperature T:

\text{Slope} = R \cdot T

Step 3

Calculation of Temperature in Kelvin

Given Slope = 25.73 L bar mol⁻¹ and R = 0.083 L bar mol⁻¹ K⁻¹:

T = \frac{\text{Slope}}{R} = \frac{25.73\;\text{L bar mol}^{-1}}{0.083\;\text{L bar mol}^{-1}\text{K}^{-1}} = 310\;\text{K}

Step 4

Conversion from Kelvin to Celsius

Converting the temperature from Kelvin to degrees Celsius:

t(^\circ\text{C}) = T(\text{K}) - 273.15 = 310 - 273 = 37^\circ\text{C}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✗ Incorrect

Verdict & Scientific Reason:

Blindly copies the numerical value of the slope as the temperature.

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Student Fallacy (Why candidates pick this trap): Assuming slope equals temperature in Celsius directly.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Calculation error from improper division.

⚠️

Student Fallacy (Why candidates pick this trap): Arithmetic miscalculation.

3 (3)

✓ 100% Correct

Verdict & Scientific Reason:

Exact conversion: 310 K - 273 = 37°C (normal human body temperature).

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Why this is airtight: None.

4 (4)

✗ Incorrect

Verdict & Scientific Reason:

Classic unit trap: 310 is the temperature in KELVIN, not Celsius!

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Student Fallacy (Why candidates pick this trap): Forgetting to convert Kelvin to Celsius.

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NTA Trap Alert: Option (4) 310°C Kelvin vs Celsius Unit Trap

310 K is calculated directly. Option (4) writes 310°C to trick students who forget to subtract 273. 310°C = 583 K, which is far too hot!

🛡️ How to avoid the -1 mark: The formula Π = CRT ALWAYS yields temperature in KELVIN. Always subtract 273 when options are in °C!

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Core NEET Syllabus Standard

Chemistry Core Physical Chemistry · Solutions Standard Benchmark

Core Scientific Principle Tested:

"Osmotic pressure is given by Π = CRT; the slope of Π vs C is RT, giving T in Kelvin."

Syllabus Focus: Colligative Properties: Osmotic Pressure and Molecular Mass Determination

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Divide slope by R to find the Kelvin pace: Subtract two-seventy-three to take body temp’s place (37°C)!

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NEET 2024 Chemistry Question 93 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Kelvin to Celsius Temperature Trap

Step-by-Step Rigorous Workflow & Mathematical Proof

Van ’t Hoff Equation for Osmotic Pressure

Identification of Graphical Slope

Calculation of Temperature in Kelvin

Conversion from Kelvin to Celsius

360° Option Elimination Engine Key Feature

NTA Trap Alert: Option (4) 310°C Kelvin vs Celsius Unit Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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