Concept:In a standard combustion analysis train, the combustion products (\( \text{H}_2\text{O} \) and \( \text{CO}_2 \)) must be trapped selectively in separate chambers so their exact masses can be measured.
Formula:$$ \text{Absorber for Water: Magnesium Perchlorate} $$
Solution:- The product gases pass through a series of absorption tubes.
- The first tube is packed with anhydrous Magnesium perchlorate, \( \text{Mg(ClO}_4)_2 \).
- This specific compound is intensely hygroscopic and acts as a powerful desiccant, physically trapping all moisture (water vapour) while letting \( \text{CO}_2 \) pass through unhindered.
- The second tube generally contains 50% KOH to chemically absorb the \( \text{CO}_2 \).
Why other options are incorrect:- \( \text{Mg(NO}_3)_2 \) & \( \text{Mg(ClO}_2)_2 \): These are not effective hygroscopic agents used in standard analytical combustion trains.
- \( \text{Mg(OH)}_2 \): This is a base (milk of magnesia) and does not function as an anhydrous desiccant.
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