Chemistry Stoichiometry UHS 2024
PMDC Verified Question 3 of 105
Number of moles in an element is directly proportional to
A
Mass of an element
B
Empirical formula mass
C
Molar mass of an element
D
Formula mass
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Mass of an element
Concept:

The relationship between moles and physical substance depends on the fundamental stoichiometric equation relating amount, mass, and molar mass.

Formula:

$$ n = \frac{m}{M} $$

Solution:

  • In the equation \( n = m / M \), \( n \) represents the number of moles, \( m \) represents the physical given mass, and \( M \) represents the constant molar mass.


  • Since \( M \) (molar mass) is a constant for any specific element, \( n \) is positioned in the numerator with respect to \( m \).


  • Therefore, as the physical mass (\( m \)) increases, the number of moles (\( n \)) increases in direct proportion.


Why other options are incorrect:

  • Molar mass of an element: Moles are inversely proportional to molar mass (it is in the denominator). A heavier element yields fewer moles for the same mass.


  • Empirical / Formula mass: These relate to compounds, not pure elements, and would also be inversely proportional regardless.

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