Chemistry Stoichiometry UHS 2023
PMDC Verified Question 27 of 105
The average weight of atoms of an element compared to the weight of one atom of ____ is called atomic weight.
A
Carbon
B
Helium
C
Hydrogen
D
Nitrogen
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Carbon
Concept:

Atomic weight (relative atomic mass) is a ratio. It compares the naturally occurring average mass of an element's isotopes to a specific fraction of a standardized reference atom.

Formula:

$$ A_r = \frac{\text{Average mass of atom}}{\frac{1}{12} \times \text{mass of Carbon-12 atom}} $$

Solution:

  • The formal definition of relative atomic weight inherently references the Carbon-12 isotope.


  • By defining Carbon-12 as weighing exactly 12.000 amu, we establish a robust comparative scale for every other element in the universe.


Why other options are incorrect:

  • Helium, Hydrogen, Nitrogen: None of these elements are the currently accepted IUPAC standard for calibrating the atomic mass unit.

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