Chemical Properties of Carbon Compounds: Combustion MCQs Quiz | Class 10
This Class X Science quiz covers Unit I: Chemical Substances – Nature and Behaviour, focusing specifically on the Chemical Properties of Carbon Compounds, with an emphasis on Combustion. Test your understanding of complete and incomplete combustion, flame characteristics, and oxidation reactions. Click Submit to view your score and download the solution PDF.
Topic Overview: Combustion of Carbon Compounds
Combustion is a chemical process in which a substance burns in the presence of oxygen to give off heat and light. For carbon compounds, this process is essentially oxidation. The nature of the flame and the products formed depend heavily on the availability of oxygen and the type of carbon compound (saturated or unsaturated).
1. Complete Combustion
When there is a sufficient supply of oxygen, carbon compounds burn completely. This typically occurs with saturated hydrocarbons (alkanes).
- Products: Carbon dioxide (CO2), Water (H2O), Heat, and Light.
- Observation: A clean, blue flame is produced.
- Equation Example: CH4 + 2O2 gives CO2 + 2H2O + Heat + Light.
2. Incomplete Combustion
If the air supply is limited, incomplete combustion occurs. This can happen even with saturated hydrocarbons if oxygen is restricted.
- Products: Carbon monoxide (CO), Water, Soot (unburnt carbon), Heat, and Light.
- Observation: A sooty, yellow flame is produced.
- Note: Unsaturated hydrocarbons (alkenes, alkynes) burn with a yellow sooty flame even in air because the percentage of carbon is higher than hydrogen, requiring more oxygen for complete combustion.
3. Formation of Coal and Petroleum
Coal and petroleum are fossil fuels formed from biomass that has been subjected to various biological and geological processes over millions of years.
- Coal: Formed from the remains of trees and other vegetation buried deep under the earth.
- Petroleum: Formed from the remains of tiny plants and animals living in the sea that sank to the bottom and were covered by silt.
4. Why Do Substances Burn with or without a Flame?
- Flame: Produced only when gaseous substances burn. Example: LPG, candle wax (vaporizes).
- Glow (No Flame): Solid substances that do not vaporize burn without a flame. Example: Charcoal burns with a red glow but no flame.
Quick Revision Table
| Type of Combustion | Oxygen Supply | Flame Color | Residue |
|---|---|---|---|
| Complete | Sufficient | Blue (Clean) | None |
| Incomplete | Limited | Yellow (Sooty) | Soot/Black smoke |
Extra Practice Questions
- Why do gas stoves have inlets for air? (Ans: To ensure sufficient oxygen for a blue flame).
- What is the poisonous gas produced during incomplete combustion? (Ans: Carbon Monoxide).
- Why does the bottom of a cooking vessel turn black? (Ans: Incomplete combustion due to blocked air holes).
- Is combustion an exothermic or endothermic reaction? (Ans: Exothermic).
- What are the products of the combustion of ethanol? (Ans: CO2, H2O, Heat, Light).
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