A catalyst acts as a negative catalyst if it ___________________?
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Answer: A. Retards the rate of reaction
Explanation
Negative catalysts, commonly referred to as inhibitors or retarders, decrease overall reaction rates. They function by increasing activation energy barriers or consuming active radical intermediates. Slowing down undesirable side reactions helps improve the selectivity of the main product. Inhibitors interrupt radical chain mechanisms by scavenging active propagation species in polymerization. Negative catalysis does not alter equilibrium positions; it only affects the rate of approach. Food preservatives often act as negative catalysts to slow down undesirable oxidation reactions.
Stabilizers are added to commercial monomers to prevent premature polymerization during storage and transport. Anti-knock agents in gasoline act as negative catalysts to suppress rapid, uncontrolled auto-ignition. Pharmaceutical formulations use inhibitors to prevent active ingredient degradation over shelf-life periods. Negative catalysts do not alter thermodynamic equilibrium constants, which depend only on temperature. Initiating reactions is the role of initiators or positive catalysts rather than negative ones. Since option A correctly defines negative catalysis, option D cannot be universally selected.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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