Chemistry Stoichiometry UHS 2024
PMDC Verified Question 1 of 105
The type and relative amount of each isotope in an element can be found by (out of syllabus)
A
R spectroscopy
B
U.V spectroscopy
C
Mass spectroscopy
D
N.M.R
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Mass spectroscopy
Concept:

Identifying isotopes requires sorting atoms based on their tiny differences in physical mass. This requires a specific analytical machine capable of deflecting ions based on their mass-to-charge (m/z) ratio.

Formula:

$$ \text{Mass Spectrometry} \rightarrow \text{Separates by m/z ratio} $$

Solution:

  • Mass spectroscopy (Spectrometry) vaporizes a sample, ionizes it, and accelerates it through a magnetic field.


  • Heavier isotopes deflect less, and lighter isotopes deflect more.


  • By mapping these deflections, a detector outputs a graph showing both the exact mass of each isotope and the relative abundance (percentage) of each in nature.


Why other options are incorrect:

  • U.V spectroscopy: Analyzes electronic transitions in molecules, useful for identifying conjugated bonds, not mass.


  • N.M.R (Nuclear Magnetic Resonance): Analyzes the magnetic properties of nuclei (like H and C-13) to determine molecular structure, but is not used to quantify generalized isotopic abundance ratios.


  • R spectroscopy: Likely a typo for IR (Infrared), which analyzes functional group vibrations, not atomic masses.

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