Rusting of iron is accelerated in: MCQ with Answer and Explanation

Rusting of iron is accelerated in:
A. Pure water without air
B. Vacuum
C. Saline water
D. Dry air
Answer: Option C
Solution (By JKSSB Mock Tests)
Saline water (containing NaCl) increases the electrical conductivity of the water, accelerating the electrochemical process of rusting. This is why ships and coastal structures rust faster. Dry air and vacuum have no moisture; pure water without dissolved oxygen slows rusting.

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Practice More chemistry Questions

Question #1
Urea is a widely used nitrogenous fertilizer. Its nitrogen content by mass is approximately:
A. 35%
B. 82%
C. 21%
D. 46%

Correct Answer: Option D


Explanation:
Urea, CO(NH₂)₂, molar mass = 60 g/mol. Mass of N = 2×14 = 28 g. Percentage N = (28/60) × 100 ≈ 46.67%, commonly rounded to 46%. It has the highest nitrogen content among solid fertilizers, making it economical. DAP (diammonium phosphate) has 18% N and 46% P₂O₅. Ammonium nitrate has 33% N. Urea is converted to ammonia and carbon dioxide by soil urease enzyme.

This question belongs to: Science chemistry
Question #2
Excessive use of chemical fertilizers can lead to:
A. Increase in beneficial soil microbes.
B. Eutrophication of water bodies.
C. Improvement of soil texture.
D. Increased soil fertility indefinitely.

Correct Answer: Option B


Explanation:
Excessive use of chemical fertilizers, especially those containing nitrogen and phosphorus, can lead to runoff into water bodies. This causes eutrophication (algal blooms), which depletes oxygen in the water and kills aquatic life. It also degrades soil health and kills beneficial microbes over time.

This question belongs to: Science chemistry
Question #3
Which of the following methods is used to obtain pure copper from impure copper?
A. Roasting
B. Smelting
C. Electrolytic refining
D. Calcination

Correct Answer: Option C


Explanation:
In electrolytic refining, impure copper is the anode, pure copper is the cathode, and CuSO₄ acidified with H₂SO₄ is the electrolyte. Copper dissolves from anode and pure copper deposits on cathode. Smelting is reduction with coke.

This question belongs to: Science chemistry