Chemistry Gases BUMHS 2022
PMDC Verified Question 42 of 65
Ideal gas equation helps to calculate the following property of ideal gas except:
A
Pressure
B
Density
C
Moles
D
Molarity
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Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Molarity
Concept:

The ideal gas equation (\( PV = nRT \)) can be manipulated to calculate various macroscopic properties of a gas, such as pressure, volume, moles, temperature, density, and molar mass.

Solution:

  • Pressure (P): Directly derived as \( P = \frac{nRT}{V} \).


  • Moles (n): Directly derived as \( n = \frac{PV}{RT} \).


  • Density (d): By substituting \( n = \frac{m}{M} \), we get \( PV = \frac{mRT}{M} \). Rearranging for density (\( m/V \)) gives \( d = \frac{PM}{RT} \).


  • Molarity: Molarity is defined as moles of solute per liter of solution (a liquid phase concept). The ideal gas law describes gases in a container, not solutes dissolved in a liquid solvent. Therefore, molarity cannot be calculated using the ideal gas equation.


Why other options are incorrect:

  • Options A, B, & C: As proven algebraically above, these are all valid properties that can be directly derived from the ideal gas equation.

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