Positive catalysts work by: MCQ with Answer and Explanation

Positive catalysts work by:
A. Decreasing activation energy
B. Consuming reactants
C. Increasing activation energy
D. Changing equilibrium
Answer: Option A
Solution (By JKSSB Mock Tests)
Catalysts lower activation energy, providing an easier pathway, thus increasing reaction rate. They do not affect equilibrium constant or get consumed.

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Practice More chemistry Questions

Question #1
The half-life of a radioactive isotope is 10 days. What fraction of the original sample remains after 30 days?
A. 1/2
B. 1/3
C. 1/4
D. 1/8

Correct Answer: Option D


Explanation:
After each half-life, half of the remaining atoms decay. Number of half-lives n = total time / half-life = 30/10 = 3. Fraction remaining = (1/2)ⁿ = (1/2)³ = 1/8. Thus 12.5% remains. Radioactive decay follows first-order kinetics. Exam trick: fraction remaining = (0.5)^(t/T), where T is half-life. After 4 half-lives, 1/16 remains.

This question belongs to: Science chemistry
Question #2
In electroplating of copper on an iron spoon, the electrolyte used is:
A. Iron sulfate
B. Sodium chloride solution
C. Copper sulfate solution
D. Sulfuric acid

Correct Answer: Option C


Explanation:
Acidified copper sulfate (CuSO₄) solution is the electrolyte. The iron spoon is the cathode, and a pure copper plate is the anode. Cu²⁺ ions are reduced at the cathode and deposited on the spoon. Fe from spoon does not go into solution because it is cathode.

This question belongs to: Science chemistry
Question #3
Mendeleev's periodic table left a gap for an element he called eka-aluminium. This element is now known as:
A. Scandium
B. Silicon
C. Germanium
D. Gallium

Correct Answer: Option D


Explanation:
Eka-aluminium was later discovered and named gallium. Eka-silicon is germanium; eka-boron is scandium. Mendeleev's predictions were remarkably accurate.

This question belongs to: Science chemistry