Question 222 marksVery Short AnswerSection B

$Distinguish between a saturated and an unsaturated hydrocarbon by flame test. List the products of combustion reaction of a saturated hydrocarbon.$

Q: Distinguish between a saturated and an unsaturated hydrocarbon by flame test. List the products of combustion reaction of a saturated hydrocarbon.

### Distinction by Flame Test 1. **Saturated Hydrocarbons:** When burnt in air, saturated hydrocarbons undergo complete combustion and burn with a **clean, blue, non-sooty flame**. 2. **Unsaturated Hydrocarbons:** When burnt in air, unsaturated hydrocarbons undergo incomplete combustion due to a higher percentage of carbon, burning with a **yellow, smoky, sooty flame**. ### Products of Combustion of a Saturated Hydrocarbon When a saturated hydrocarbon (such as methane, $\mathrm{CH_4}$) undergoes complete combustion in the presence of oxygen, the products formed are: - Carbon dioxide ($\mathrm{CO_2}$) - Water vapour ($\mathrm{H_2O}$) - Heat and light $$\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + Heat\ and\ Light}$$

Carbon and its Compounds

Saturated and Unsaturated Carbon Compounds

Official answer

\mathrm{CH_4}

clean blue flame

sooty flame

yellow flame

carbon dioxide

water

heat and light

complete combustion

Marking scheme

1. $Distinction between saturated and unsaturated hydrocarbons using flame test (clean blue flame vs. yellow sooty flame) (1 mark)$
2. $Listing the products of combustion of a saturated hydrocarbon (Carbon dioxide, water, heat, and light) (1 mark)$

Hint

$Think about the difference in the soot produced during combustion and write down the standard products of burning a fuel like methane.$

Quick oral answer

$Saturated hydrocarbons burn with a clean blue flame, while unsaturated ones burn with a yellow sooty flame. The products of complete combustion are carbon dioxide, water, heat, and light.$

Common mistakes

1. $Confusing the flame colors of saturated and unsaturated hydrocarbons.$
2. $Forgetting to mention 'heat and light' as products of a combustion reaction.$

Analysis and explanation

Saturated hydrocarbons contain only single covalent bonds and have a lower carbon-to-hydrogen ratio, allowing them to burn completely in the presence of atmospheric oxygen to produce a clean blue flame. Unsaturated hydrocarbons contain double or triple bonds and have a higher carbon content by mass. The oxygen in the air is insufficient for their complete combustion, leaving unburnt carbon particles that glow yellow and escape as black soot.

Interesting facts

$If the air holes of a gas burner are blocked, even saturated hydrocarbons (like LPG) start burning with a yellow, sooty flame because of a limited supply of oxygen, which blackens the bottoms of cooking vessels.$

Question details

Q22 of 39 questions

Board: CBSE
Class: Class 10
Subject: Science
Year: 2024
Section: Section B
Marks: 2
Type: Very Short Answer
Chapter: Carbon and its Compounds
Topic: $Saturated and Unsaturated Carbon Compounds$
Bloom's level: Understanding
Syllabus topic: $Saturated and unsaturated carbon compounds, Combustion$

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Frequently asked questions

$How many marks does this question carry in CBSE Class 10 Science 2024?$

$This question carries 2 marks in the CBSE Class 10 Science 2024 examination.$

$Which chapter does this question come from in Science?$

$This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.$

$What topic does this question cover in Science?$

$This question covers the topic "Saturated and Unsaturated Carbon Compounds" from CBSE Class 10 Science.$

$What type of question is this in the CBSE Class 10 Science 2024 paper?$

$This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.$