NEET 2018 Chemistry Questions with Answers and Explanation (1–10)

🧪 NEET 2018 Chemistry Questions with Answers & Explanations (Part 1)

Here are the first 10 Chemistry questions from NEET 2018, with correct answers and full explanations to help you understand the concepts better.

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🔹 Question 1:

Which one is the correct order of basic strength?

• (a) NH₃ < CH₃NH₂ < (CH₃)₂NH < (CH₃)₃N
• (b) CH₃NH₂ < NH₃ < (CH₃)₂NH < (CH₃)₃N
• (c) NH₃ < CH₃NH₂ < (CH₃)₃N < (CH₃)₂NH
• (d) (CH₃)₃N < (CH₃)₂NH < CH₃NH₂ < NH₃

✅ Answer: (a)

Explanation: Basic strength increases with electron-donating alkyl groups. More methyl groups → higher basicity. So: NH₃ < CH₃NH₂ < (CH₃)₂NH < (CH₃)₃N.

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🔹 Question 2:

The rate of a reaction becomes four times when the concentration of reactant is doubled. The order of the reaction is:

• (a) 0
• (b) 1
• (c) 2
• (d) 3

✅ Answer: (c)

Explanation: Rate ∝ [A]^n. If rate becomes 4× when [A] is doubled, then 2ⁿ = 4 ⇒ n = 2 (second-order reaction).

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🔹 Question 3:

Which of the following is a nucleophile?

• (a) BF₃
• (b) NH₃
• (c) H⁺
• (d) NO⁺

✅ Answer: (b)

Explanation: NH₃ has a lone pair on nitrogen and can donate it, making it a good nucleophile.

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🔹 Question 4:

Which among the following is the most acidic?

• (a) Water
• (b) Ethanol
• (c) Acetic acid
• (d) Phenol

✅ Answer: (c)

Explanation: Acetic acid is a carboxylic acid and shows much higher acidity compared to alcohols and phenols due to resonance stabilization of acetate ion.

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🔹 Question 5:

The correct order of decreasing bond dissociation enthalpy of C–X bond (X = halogen) in methyl halides is:

• (a) CH₃F > CH₃Cl > CH₃Br > CH₃I
• (b) CH₃I > CH₃Br > CH₃Cl > CH₃F
• (c) CH₃Cl > CH₃F > CH₃Br > CH₃I
• (d) CH₃Br > CH₃Cl > CH₃F > CH₃I

✅ Answer: (a)

Explanation: As halogen size increases, bond length increases and bond dissociation energy decreases. Hence, C–F > C–Cl > C–Br > C–I.

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🔹 Question 6:

The metal that cannot be obtained by electrolysis of its aqueous salt solution is:

• (a) Cu
• (b) Cr
• (c) Ag
• (d) Zn

✅ Answer: (b)

Explanation: Chromium has a high reduction potential and reacts with water; it cannot be obtained from aqueous solution by electrolysis.

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🔹 Question 7:

Which of the following is least likely to behave as Lewis base?

• (a) CO
• (b) F⁻
• (c) Cl⁻
• (d) BF₃

✅ Answer: (d)

Explanation: BF₃ is an electron-deficient molecule and acts as a Lewis acid, not a base.

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🔹 Question 8:

The correct statement for the molecule C₆₀ is:

• (a) It has 20 six-membered rings and 12 five-membered rings
• (b) It is a planar molecule
• (c) It has 12 six-membered rings and 20 five-membered rings
• (d) Each carbon is bonded to 3 other carbon atoms

✅ Answer: (a)

Explanation: C₆₀ (buckminsterfullerene) has 20 hexagons and 12 pentagons. Each carbon is sp² hybridized and bonded to 3 carbon atoms.

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🔹 Question 9:

Which of the following is not an example of a chain-growth polymer?

• (a) Teflon
• (b) Polyvinyl chloride
• (c) Bakelite
• (d) Polystyrene

✅ Answer: (c)

Explanation: Bakelite is a thermosetting polymer and is formed by step-growth (condensation) polymerization, not chain-growth (addition).

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🔹 Question 10:

In Freundlich adsorption isotherm, the value of 1/n is:

• (a) 0 in case of physical adsorption
• (b) Between 0 and 1 in all cases
• (c) 1 in case of chemisorption
• (d) Greater than 1 in all cases

✅ Answer: (b)

Explanation: Freundlich isotherm: x/m = kP^1/n, where 1/n is between 0 and 1 indicating favorable adsorption.

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📌 Continue to: Part 2 – Questions 11–20