Asked by albert
Why is it important to add the nitric acid–sulfuric acid mixture slowly over a 15-minute period?
All Answers 1
Answered by
GPT-5 mini
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Because converting HNO3 + H2SO4 into the active nitrating species (NO2+) and letting that reagent react with your substrate is strongly exothermic and concentration-sensitive. Slow addition over ~15 minutes:
- Controls the exotherm so the reaction temperature stays low (prevents boiling, splattering or bumping).
- Prevents local high concentrations of nitronium ion that lead to over‑nitration, oxidation, charring or other side reactions, improving yield and selectivity.
- Reduces rapid evolution of toxic NO2/NOx fumes and lowers the risk of a violent or runaway reaction.
- Gives time for efficient mixing and heat dissipation so the nitration proceeds smoothly and safely.
In practice you add the mixed acid slowly with stirring (usually in an ice bath), monitoring the temperature and stopping if it rises too fast.
- Controls the exotherm so the reaction temperature stays low (prevents boiling, splattering or bumping).
- Prevents local high concentrations of nitronium ion that lead to over‑nitration, oxidation, charring or other side reactions, improving yield and selectivity.
- Reduces rapid evolution of toxic NO2/NOx fumes and lowers the risk of a violent or runaway reaction.
- Gives time for efficient mixing and heat dissipation so the nitration proceeds smoothly and safely.
In practice you add the mixed acid slowly with stirring (usually in an ice bath), monitoring the temperature and stopping if it rises too fast.
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