Q.100 Chemistry ⭐ 360° Option Elimination Active

NEET 2023 Chemistry Question 100 Solution

Topic: Environmental Chemistry · Official NTA Booklet Code G5

Question

Given below are two statements: Statement I: The nutrient deficient water bodies lead to eutrophication. Statement II: Eutrophication leads to decrease in the level of oxygen in the water bodies. In the light of the above statements, choose the correct answer from the options given below:

(1)Statement I is incorrect but Statement II is true.
(2)Both Statement I and Statement II are true.
(3)Both Statement I and Statement II are false.
(4)Statement I is correct but Statement II is false.

✓

Verified Against NTA Final Answer Key

Option (1) : Statement I is incorrect but Statement II is true.

📚 Environmental Chemistry Easy

📋 Given Parameters & Problem Setup

Statement I The nutrient deficient water bodies lead to eutrophication.

Statement II Eutrophication leads to decrease in the level of oxygen in the water bodies.

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The 30-Second Exam Hall Shortcut: ⚡ Definition Check: Eutrophication Means Nutrient ENRICHED, Not Deficient!

⏱️ Save ~25 seconds

By canonical definition, eutrophication is the process in which water bodies become nutrient-ENRICHED (excess nitrates and phosphates from runoff), causing massive algal bloom! Hence Statement I is INCORRECT. Algae die and decay aerially, consuming dissolved oxygen and suffocating aquatic life! Hence Statement II is TRUE. Verdict: Statement I is incorrect but Statement II is true (Option 1) in 10 seconds!

1 Check Statement I: "The nutrient deficient water bodies lead to eutrophication." False! Eutrophication is caused by nutrient-rich (nutrient-enriched) water bodies, particularly phosphates and nitrates.

2 Check Statement II: "Eutrophication leads to decrease in the level of oxygen in the water bodies." True! Dense algal bloom prevents sunlight, and microbial decomposition of dead algae depletes dissolved oxygen (BOD surges, DO plummets).

3 Match: Statement I is incorrect but Statement II is true (Option 1).

🛡️

Why You Can 100% Trust This Shortcut: Verbatim NCERT Environmental Chemistry section on Water Pollution & Eutrophication.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Definition of Eutrophication

Eutrophication is defined as the process in which a water body becomes overly enriched with nutrients (primarily phosphates and nitrates from agricultural runoff, fertilizers, and sewage):

\text{Eutrophication} \iff \text{Nutrient \textbf{enrichment}} \; (\text{NOT nutrient deficiency})

Step 2

Evaluate Statement I

Statement I asserts that "nutrient deficient water bodies lead to eutrophication." This directly contradicts the canonical definition, as oligotrophic (nutrient-deficient) waters support low biological productivity and do NOT undergo eutrophication. Statement I is INCORRECT:

\text{Statement I} = \text{INCORRECT (requires nutrient-rich waters)}

Step 3

Mechanism of Dissolved Oxygen Depletion (Statement II)

Nutrient enrichment stimulates explosive growth of algae (algal bloom). When the dense algal mass dies, aerobic bacteria consume enormous quantities of dissolved oxygen to decompose the dead organic matter. Consequently, the concentration of dissolved oxygen (DO) plummets below critical levels, killing fish and other aquatic organisms. Statement II is TRUE:

\text{Algal decay} + \text{Aerobic bacteria} \implies \text{BOD increases, Dissolved } \text{O}_2 \text{ decreases}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✓ 100% Correct

Verdict & Scientific Reason:

Accurate: Eutrophication is driven by nutrient enrichment (making I false), which subsequently depletes dissolved oxygen (making II true).

💡

Why this is airtight: None. Candidate read the critical word "deficient" carefully.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Statement I is false because nutrient-deficient waters do not cause eutrophication.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate skimmed the statement and assumed "nutrient" implied nutrient-rich.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Statement II is factually true; oxygen levels dramatically decrease due to algal decomposition.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate doubted that eutrophication causes dissolved oxygen depletion.

4 (4)

✗ Incorrect

Verdict & Scientific Reason:

Completely inverts the truth values of both statements.

⚠️

Student Fallacy (Why candidates pick this trap): Candidate reversed the concepts of nutrient enrichment and oxygen depletion.

⚠️

NTA Trap Alert: Misreading "Nutrient Deficient" as "Nutrient Enriched"

Under exam pressure, students read the word "nutrient" and quickly assume Statement I says "nutrient rich". Look closely at the word "deficient" — that single opposite word makes Statement I completely false!

🛡️ How to avoid the -1 mark: Read every qualifying word carefully: "deficient" vs "enriched".

📖

Core NEET Syllabus Standard

National Eligibility cum Entrance Test (NEET UG) · Environmental Chemistry Standard Benchmark

Core Scientific Principle Tested:

"Eutrophication is the aging of water bodies due to nutrient enrichment, leading to algal blooms and drastic loss of dissolved oxygen."

Syllabus Focus: Water Pollution – Eutrophication and Biochemical Oxygen Demand (BOD)

Preserved in Rationalized Curriculum Syllabus & Academic Standards ↗

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NEET 2023 Chemistry Question 100 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Definition Check: Eutrophication Means Nutrient ENRICHED, Not Deficient!

Step-by-Step Rigorous Workflow & Mathematical Proof

Definition of Eutrophication

Evaluate Statement I

Mechanism of Dissolved Oxygen Depletion (Statement II)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Misreading "Nutrient Deficient" as "Nutrient Enriched"

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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Atmospheric Reactions: Acid Rain, Photochemical Smog, Ozone Depletion, Tropospheric Pollution

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