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Questions and Answers
Which gas is collected at the cathode during the electrolysis of water?
Which gas is collected at the cathode during the electrolysis of water?
Which material is used as electrodes in the electrolysis of water experiment?
Which material is used as electrodes in the electrolysis of water experiment?
What is the correct formula that represents the decomposition of water during electrolysis?
What is the correct formula that represents the decomposition of water during electrolysis?
What observation confirms the presence of oxygen gas at the anode?
What observation confirms the presence of oxygen gas at the anode?
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What is the purpose of adding dilute sulphuric acid to water in the electrolysis experiment?
What is the purpose of adding dilute sulphuric acid to water in the electrolysis experiment?
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Which terminal of the battery should be connected to the anode in the setup?
Which terminal of the battery should be connected to the anode in the setup?
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What happens at the cathode during electrolysis of water?
What happens at the cathode during electrolysis of water?
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What is the explanation for the volume of hydrogen gas collected being double that of oxygen gas?
What is the explanation for the volume of hydrogen gas collected being double that of oxygen gas?
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Why is it necessary to use a wide-mouthed glass bottle in the electrolysis setup?
Why is it necessary to use a wide-mouthed glass bottle in the electrolysis setup?
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What observation indicates the formation of hydrogen gas?
What observation indicates the formation of hydrogen gas?
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Study Notes
Electrolysis of Water
- Water decomposes into hydrogen and oxygen gas when electric current is passed through acidified water.
- The reaction can be represented as: 2H2O(l)⟶2H2(g)+O2(g)2H_2O(l) \longrightarrow 2H_2(g) + O_2(g)2H2O(l)⟶2H2(g)+O2(g)
Experimental Setup
- A wide-mouthed glass bottle with a removed bottom is used, fixed on a stand in an inverted position.
- A rubber cork with two holes is fitted in the neck of the bottle, with two carbon rods (or graphite rods) fixed in the holes tightly.
- The glass bottle is filled two-thirds with water, and a few drops of dilute sulphuric acid are added to make water a good conductor of electricity.
Procedure
- Two similar test-tubes filled with water are inverted over the two carbon electrodes, keeping them initially filled with water.
- The outer ends of carbon rods are connected to the two terminals (+) and (-) of a 6 volt battery by wires having a switch.
- The left-side carbon rod is connected to the (+) terminal of the battery, and the right-side carbon rod is connected to the (-) terminal of the battery.
- When the switch is closed, gas bubbles are formed at both carbon electrodes.
Observation and Testing
- Gas bubbles formed at the left-side carbon electrode (connected to the (+) terminal) are of oxygen, which can be tested by bringing a glowing splinter near the mouth of the test-tube, causing it to burst into flame.
- Gas bubbles formed at the right-side carbon electrode (connected to the (-) terminal) are of hydrogen, which can be tested by bringing a burning candle near the mouth of the test-tube, causing it to extinguish.
Conclusion
- When electricity is passed through water, it decomposes to give hydrogen and oxygen gas.
- The volume of hydrogen gas collected at the cathode is double the volume of oxygen gas collected at the anode, which is in accordance with the formula of water, H2O.
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Description
Learn about the decomposition of water into hydrogen and oxygen through electrolysis, a reaction driven by electric current.
