Q.130 Chemistry ⭐ 360° Option Elimination Active

NEET 2020 Chemistry Question 130 Solution

Topic: Hydrogen · Official NTA Booklet Code E1

Question

Match the following and identify the correct option. (a) CO(g)+H2(g) (i) Mg(HCO3)2+ Ca(HCO3)2 (b) Temporary (ii) An electron hardness of deficient hydride water (c) B2H6 (iii) Synthesis gas (d) H2O2 (iv) Non-planar structure (a) (b) (c) (d)

(1)(iii) (i) (ii) (iv)
(2)(iii) (ii) (i) (iv)
(3)(iii) (iv) (ii) (i)
(4)(i) (iii) (ii) (iv)

✓

Verified Against NTA Final Answer Key

Option (1) : (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)

📚 Hydrogen Easy

📋 Given Parameters & Problem Setup

Column I (Substances/Concepts) (a) CO(g) + H2(g), (b) Temporary hardness of water, (c) B2H6, (d) H2O2

Column II (Descriptions) (i) Mg(HCO3)2 + Ca(HCO3)2, (ii) An electron deficient hydride, (iii) Synthesis gas, (iv) Non-planar structure

⚡

The 30-Second Exam Hall Shortcut: ⚡ "CO + H2 = Syngas; Hardness = Bicarbonates; B2H6 = Electron Deficient; H2O2 = Open-Book Non-Planar!"

⏱️ 20 seconds

CO + H2 is Synthesis gas / water gas (a->iii). Temporary hardness is caused by bicarbonates of magnesium and calcium (b->i). Diborane B2H6 is an electron deficient hydride with 3c-2e banana bonds (c->ii). H2O2 has a non-planar open-book structure (d->iv). Match gives Option (1) in 5 seconds!

1 CO(g) + H2(g) is known as Synthesis gas or syngas -> (a)-(iii).

2 Temporary hardness of water is due to Mg(HCO3)2 and Ca(HCO3)2 -> (b)-(i).

3 B2H6 (diborane) is a classic electron-deficient hydride -> (c)-(ii).

4 H2O2 has a non-planar open-book structure with dihedral angle 111.5° (gas) -> (d)-(iv).

5 Mapping: (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv) -> Option 1.

🛡️

Why You Can 100% Trust This Shortcut: NCERT Chemistry · Hydrogen (Water Gas, Hardness of Water, Hydrides & Hydrogen Peroxide Structure)

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Match CO(g) + H2(g)

The equimolar mixture of $\text{CO}$ and $\text{H}_2$ is called water gas or synthesis gas ('syngas') because it is widely used in the synthesis of methanol and a number of hydrocarbons. Thus, (a) matches (iii).

Step 2

Match Temporary Hardness of Water

Temporary hardness of water is caused by the presence of soluble bicarbonates (hydrogen carbonates) of calcium and magnesium, namely $\text{Ca(HCO}_3)_2$ and $\text{Mg(HCO}_3)_2$ , which precipitate as carbonates on boiling. Thus, (b) matches (i).

Step 3

Match Diborane (B2H6)

Diborane ( $\text{B}_2\text{H}_6$ ) has 12 valence electrons, insufficient to form conventional 2-center 2-electron bonds for all atoms, requiring two 3-center 2-electron ( $3c-2e$ ) B-H-B banana bonds. It is classified as an electron-deficient hydride. Thus, (c) matches (ii).

Step 4

Match Hydrogen Peroxide (H2O2)

Hydrogen peroxide has a non-planar structure resembling an open book, with the two O-H bonds located on different intersecting planes with a dihedral angle of $111.5^\circ$ in the gas phase and $90.2^\circ$ in crystalline phase. Thus, (d) matches (iv).

⭐

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 A

✓ 100% Correct

Verdict & Scientific Reason:

Accurate pairing across all four hydrogen and hydride concepts.

💡

Why this is airtight: None; textbook matching.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; claims temporary hardness is an electron deficient hydride.

⚠️

Student Fallacy (Why candidates pick this trap): Swapping items (b) and (c).

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; assigns non-planar structure to temporary hardness.

⚠️

Student Fallacy (Why candidates pick this trap): Arbitrary matching error.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; claims CO + H2 is temporary hardness.

⚠️

Student Fallacy (Why candidates pick this trap): Swapping syngas and temporary hardness.

⚠️

NTA Trap Alert: Temporary vs Permanent Hardness Salts

- TEMPORARY hardness: Bicarbonates ( $\text{Ca(HCO}_3)_2, \text{Mg(HCO}_3)_2$ ). - PERMANENT hardness: Chlorides and Sulphates ( $\text{CaCl}_2, \text{MgCl}_2, \text{CaSO}_4, \text{MgSO}_4$ ).

🛡️ How to avoid the -1 mark: Temporary = Bicarbonates! Permanent = Chlorides and Sulphates!

📖

Core NEET Syllabus Standard

Chemistry · Hydrogen Standard Benchmark

Core Scientific Principle Tested:

Syllabus Focus: Hydrogen Compounds Match: Syngas, Temporary Hardness, Diborane & H2O2 Structure

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2020 Chemistry Question 130 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ "CO + H2 = Syngas; Hardness = Bicarbonates; B2H6 = Electron Deficient; H2O2 = Open-Book Non-Planar!"

Step-by-Step Rigorous Workflow & Mathematical Proof

Match CO(g) + H2(g)

Match Temporary Hardness of Water

Match Diborane (B2H6)

Match Hydrogen Peroxide (H2O2)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Temporary vs Permanent Hardness Salts

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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