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Questions and Answers
What is the primary component of air that supports combustion?
What is the primary component of air that supports combustion?
- Oxygen (correct)
- Nitrogen
- Water Vapor
- Carbon Dioxide
Which gas comprises approximately 78% of the air's composition?
Which gas comprises approximately 78% of the air's composition?
- Oxygen
- Carbon Dioxide
- Nitrogen (correct)
- Argon
In the experiment with a burning candle, what happens to the sodium hydroxide solution as oxygen is consumed?
In the experiment with a burning candle, what happens to the sodium hydroxide solution as oxygen is consumed?
- It rises in the gas jar.
- It drops in the gas jar. (correct)
- It evaporates completely.
- It remains unchanged.
What is the reason for using sodium hydroxide instead of water in the combustion experiments?
What is the reason for using sodium hydroxide instead of water in the combustion experiments?
What does the final volume in the combustion experiments indicate?
What does the final volume in the combustion experiments indicate?
In the oxidation of copper experiment, what happens to the copper when heated with air?
In the oxidation of copper experiment, what happens to the copper when heated with air?
Why is it necessary to allow gases to cool in combustion experiments?
Why is it necessary to allow gases to cool in combustion experiments?
What is a common source of error in experiments measuring active air?
What is a common source of error in experiments measuring active air?
What does combustion produce besides carbon dioxide?
What does combustion produce besides carbon dioxide?
What happens to the color of heated copper during the oxidation process?
What happens to the color of heated copper during the oxidation process?
In a combustion experiment, what is concluded when the candle goes out?
In a combustion experiment, what is concluded when the candle goes out?
Why is excess copper used in the oxidation experiment?
Why is excess copper used in the oxidation experiment?
How is the percentage of active air calculated in the combustion experiments?
How is the percentage of active air calculated in the combustion experiments?
What is produced as a result of the reaction between copper and oxygen?
What is produced as a result of the reaction between copper and oxygen?
Flashcards
Combustion
Combustion
A process where substances combine with oxygen to produce heat.
Active part of air
Active part of air
The part of air that supports combustion. It's mostly oxygen.
Inactive part of air
Inactive part of air
The part of air that does not support burning. It's mostly nitrogen.
Percentage of oxygen in air
Percentage of oxygen in air
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Burning candle experiment
Burning candle experiment
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Sodium Hydroxide role
Sodium Hydroxide role
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Initial volume of air
Initial volume of air
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Final volume of air
Final volume of air
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Oxidation of Copper
Oxidation of Copper
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Cotton role (in Copper Oxidation)
Cotton role (in Copper Oxidation)
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Percentage of Active Air (Copper)
Percentage of Active Air (Copper)
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Source of error (Candle exp)
Source of error (Candle exp)
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Source of error (Copper exp)
Source of error (Copper exp)
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Constituents of air
Constituents of air
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Variable components
Variable components
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Study Notes
Combustion and Air Composition
- Air is a mixture of gases, not a compound. It can be separated into its constituent gases by physical means.
- Air's components exist in specific proportions.
- Air exhibits the properties of its individual components.
- Air is crucial for various processes, including synthesis, respiration, and fuel combustion.
Air Composition Table
- Nitrogen: 78% by volume
- Oxygen: 20.9% by volume
- Carbon oxides: 0.03% by volume
- Noble gases: 0.497% by volume
- Water vapor: Variable
- Dust particles: Variable
Active and Inactive Parts of Air
- Active part: Supports combustion; mainly oxygen.
- Inactive part: Does not support combustion; mainly nitrogen.
Combustion Definition
- Combustion: Substances combine with oxygen, producing heat.
Percentage of Active Air Experiments
Burning Candle in Fixed Volume of Air
- Goal: Determine the percentage of active air (oxygen).
- Setup: Candle, graduated trough, sodium hydroxide solution, fixed volume container (e.g., a beaker or flask)
- Experiment Procedure:
- A candle is lit inside the fixed volume of air.
- Sodium hydroxide absorbs the carbon dioxide produced by the burning candle.
- The level of sodium hydroxide solution will rise as oxygen is consumed.
- Observations: The candle goes off due to oxygen depletion. The level of the sodium hydroxide solution in the trough rises as oxygen is consumed.
- Calculation: Percentage Active Air = [(Initial Volume – Final Volume)/Initial Volume] x 100%
- Critical Note: Final reading should be taken once the apparatus has cooled. Gases expand when heated, so cooling ensures accurate volume measurement.
- Possible Errors: Sodium hydroxide may not fully absorb the carbon dioxide, the candle might extinguish before using up all available oxygen, and incomplete combustion introduces errors.
Oxidation of Copper in Fixed Volume of Air
- Goal: Determine the percentage of active air (oxygen).
- Setup: Syringe with air, container for copper, combustion tube, cotton.
- Experiment Procedure:
- Air is passed over heated copper slowly and repeatedly.
- The heated copper reacts with oxygen in the air to produce copper oxide (a black solid).
- Cotton is used to prevent copper from entering other parts of the apparatus.
- Observations: The copper changes from reddish-brown to black solid.
- Calculation: Percentage Active Air = [(Initial Volume – Final Volume)/Initial Volume] x 100%
- Possible Errors: Heated copper may not use all the oxygen, air leakage, and not accounting for the tube's volume.
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