NTSE Chemistry: Assertion–Reason in 59 Sec 💡

 

❓ Question

Assertion (A): Elements and compounds are examples of pure substances.
Reason (R): The properties of a compound are different from those of its constituent elements.

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🖼️ Question Image

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✍️ Short Solution

This is a pure concept + logic-based assertion–reason question.
No calculation — just definition clarity + reasoning check 💯

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🔹 Step 1 — Check Assertion (A) (MOST IMPORTANT 💯)

Assertion:
👉 Elements and compounds are pure substances

✔️ TRUE

👉 Kyun?

• Pure substance ⇒ fixed composition + uniform properties
• Elements → same type of atoms
• Compounds → fixed ratio of elements

📌 Dono hi pure substances hote hain ✅

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🔹 Step 2 — Check Reason (R)

Reason:
👉 Properties of compound ≠ properties of constituent elements

✔️ TRUE

Example:

• Hydrogen → inflammable 🔥
• Oxygen → supports combustion
• Water → extinguishes fire

📌 Completely different properties ✔️

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🔹 Step 3 — Link Between A and R

👉 Ab sabse important step:

Kya R, A ko explain karta hai?

❌ NO

👉 Kyun?

• Assertion based hai:

  $$\text{Fixed composition}$$
  

• Reason based hai:

  $$\text{Property change}$$
  

👉 Dono different concepts hain ⚠️

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🔹 Step 4 — Final Logic

• A → TRUE ✅
• R → TRUE ✅
• R explains A → FALSE ❌

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🔹 Step 5 — NTSE Golden Traps

❌ Dono true dekh ke option (a) tick kar dena
❌ “Property change = purity” assume kar lena
❌ Composition aur properties ko mix kar dena

⚠️ Golden Rule:

Assertion–Reason me “connection” check karo, sirf correctness nahi

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✅ Final Answer

$$\boxed{\text{Both A and R are true, but R is NOT the correct explanation of A}}$$

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⭐ Golden NTSE Insight

• Pure substance ⇒ fixed composition
• Compound ⇒ chemical combination in definite ratio
• Property change ⇒ new substance formation (different concept)

🧠 One-line memory:

Correct + correct ≠ explanation always