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#combustion

20 public questions tagged with this topic.

A hydrocarbon with 9 σ bonds produces 5 moles of CO₂ per mole upon combustion. What is its molecular formula?

5 carbons (from 5 CO₂). CH₃CH₂CH₂CH₂CH₃ (pentane) has 9 σ (8 C-H, 1 C-C from single bonds), no π, and fits C₅H₁₂.

Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Fundamental Concepts - Reaction Mechanism - Fission and Reaction Intermediates

What volume of CO₂ at STP is produced when 10 g of C₄H₁₀ is burned completely? (Molar mass: C₄H₁₀ = 58 g/mol)

Reaction: 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O. Moles of C₄H₁₀ ≈ 0.1724 mol. 2 mol produce 8 mol CO₂; 0.1724 mol produce ≈ 0.6896 mol. Volume = 0.6896 × 22.4 ≈ 15.45 L.

Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Stoichiometry and Stoichiometric Calculations and Limiting Reagent

What volume of CO₂ at STP is produced when 15 g of C₃H₆ is burned completely? (Molar mass: C₃H₆ = 42 g/mol)

Reaction: 2C₃H₆ + 9O₂ → 6CO₂ + 6H₂O. Moles of C₃H₆ = 15/42 ≈ 0.3571 mol. 2 mol C₃H₆ produce 6 mol CO₂; 0.3571 mol produce ≈ 1.0714 mol. Volume = 1.0714 × 22.4 ≈ 24 L.

Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Stoichiometry and Stoichiometric Calculations and Limiting Reagent

What volume of O₂ at STP is required to burn 7.8 g of C₃H₆ completely to CO₂ and H₂O? (Molar mass: C₃H₆ = 42 g/mol)

Reaction: 2C₃H₆ + 9O₂ → 6CO₂ + 6H₂O. Moles of C₃H₆ ≈ 0.1857 mol. 2 mol need 9 mol O₂; 0.1857 mol need ≈ 0.8357 mol. Volume = 0.8357 × 22.4 ≈ 18.72 L.

Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Reactions in Solutions and Mass Percentage and Numericals

A 0.98 g sample of a hydrocarbon produces 3.08 g of CO₂ and 1.26 g of H₂O on complete combustion. What is its molecular

Mass of C ≈ 0.84 g; mass of H = 0.14 g. Total = 0.98 g. Moles: C = 0.07, H = 0.14; ratio = 1 : 2; empirical formula = CH₂, mass = 14 g/mol. n = 98/14 = 7; molecular formula = C₇H₁₄.

Ref: NCERT Class 11 Chemistry > Chapter 1: Some Basic Concepts of Chemistry > Topic: Mole Concept and Molar Masses and Percentage Composition