Chemistry Quiz jee mains pyQ 2021

🧪 Chemistry Concept Quiz

Try solving each question before revealing the answer. Great for JEE and NEET preparation!

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1️⃣ Species with One Unpaired Electron

Question: How many of the following have one unpaired electron — N₂, O₂⁺, O₂⁻, C₂, H₂, CN, He₂⁺?

Answer: 4 (C₂, O₂, H₂, He₂⁺)

2️⃣ Ambidentate Ligands

Question: Among NO₂⁻, SCN⁻, C₂O₄²⁻, NH₃, CN⁻, SO₄²⁻, H₂O — how many are ambidentate?

Answer: 3 (NO₂⁻, SCN⁻, CN⁻) — each has two different donor atoms.

3️⃣ Colourless Lanthanoid Ions

Question: Which of Eu³⁺, Lu³⁺, Nd³⁺, La³⁺, Sm³⁺ are colourless?

Answer: 2 (La³⁺ and Lu³⁺) — no unpaired 4f electrons.

4️⃣ Essential Amino Acids

Question: How many of the following are essential: Arginine, Phenylalanine, Aspartic acid, Cysteine, Histidine, Valine, Proline?

Answer: 4 (Arginine, Phenylalanine, Histidine, Valine)

5️⃣ Neutralization Heat Ratio

Question: Equal volumes of 1M HCl and 1M H₂SO₄ are neutralized by 1M NaOH. If heats liberated are X and Y respectively, find Y/X.

Answer: 2 — H₂SO₄ releases double the H⁺ ions per mole.

6️⃣ Oxidation by Dichromate

Question: Which of Fe, Ni, Ag, Au will be oxidized by Cr₂O₇²⁻ in acidic medium?

Answer: 3 (Fe, Ni, Ag) — all have lower reduction potential than dichromate.

7️⃣ Molality of CuSO₄ Solution

Question: A 0.2 M CuSO₄ solution (density 1.25 g/mL, volume 500 mL). Find molality (m).

Answer: ≈ 164 × 10⁻³ mol/kg

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