A catalyst that slows down a reaction is called: MCQ with Answer and Explanation

A catalyst that slows down a reaction is called:
A. Biocatalyst
B. Negative catalyst (inhibitor)
C. Autocatalyst
D. Positive catalyst
Answer: Option B
Solution (By JKSSB Mock Tests)
A negative catalyst (inhibitor) decreases the rate of a reaction by increasing activation energy or destroying active intermediates. Example: phosphoric acid inhibits H₂O₂ decomposition. Positive catalysts speed up, enzymes are biocatalysts, autocatalysts are products that catalyze their own formation.

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Practice More chemistry Questions

Question #1
The combined gas law is represented by:
A. PV = constant
B. P₁V₁/T₁ = P₂V₂/T₂
C. V/T = constant
D. PV = nRT

Correct Answer: Option B


Explanation:
Combined gas law combines Boyle's, Charles', and Gay-Lussac's laws for a fixed mass of gas. It relates P, V, T when all change. PV=nRT is ideal gas equation for n moles.

This question belongs to: Science chemistry
Question #2
The process of extracting a metal by heating its oxide ore with a reducing agent is called:
A. Smelting
B. Leaching
C. Calcination
D. Roasting

Correct Answer: Option A


Explanation:
Smelting involves heating a metal oxide ore (roasted or calcined) with a reducing agent like coke (carbon) or CO to obtain the metal in the molten state. Example: Fe₂O₃ + 3CO → 2Fe + 3CO₂ in blast furnace. Calcination: heating carbonate/ hydroxide ore in absence of air. Roasting: heating sulfide ore in excess air. Leaching: chemical dissolution of ore. Smelting is a key pyrometallurgical step.

This question belongs to: Science chemistry
Question #3
An enzyme is a:
A. Proteinaceous biocatalyst
B. Negative catalyst
C. Lipid catalyst
D. Inorganic catalyst

Correct Answer: Option A


Explanation:
Enzymes are proteinaceous substances that act as biological catalysts, speeding up biochemical reactions in living organisms without being consumed. They are highly specific and work under mild conditions (pH, temperature). Examples: amylase breaks down starch, pepsin digests proteins. Inorganic catalysts are like Pt, Ni. Lipids are fats, not catalysts. Negative catalysts (inhibitors) slow reactions. Enzymes may be deactivated by high temperature or extreme pH.

This question belongs to: Science chemistry