Zerlegung von Wasser - Die Elektrolyse von Wasser

Herr Weiner

10 May 202110:15

Summary

TLDRIn this educational video, the host demonstrates the electrolysis of water using a Hoffmann apparatus. By applying 20 volts, water is split into hydrogen and oxygen gases. The experiment confirms that hydrogen forms at the cathode and oxygen at the anode. The host verifies the gases using a spark test for oxygen and a pop test for hydrogen, showing that water indeed consists of hydrogen and oxygen.

Takeaways

🔬 Electrolysis is the process of breaking down a substance into its constituent elements using electrical current or voltage.
💧 Water electrolysis involves splitting water into hydrogen and oxygen gases.
🔌 The Hoffmann electrolysis apparatus is used in the demonstration to show the electrolysis of water.
🔋 A voltage of around 20 volts is applied to the water in the apparatus to initiate the electrolysis.
📈 Hydrogen gas is produced at the cathode (negative electrode), while oxygen gas is produced at the anode (positive electrode).
🔥 A glowing splint test is used to confirm the presence of oxygen, as oxygen supports combustion.
💥 The 'knallgas' (pop test) is used to demonstrate the presence of hydrogen, which is flammable and reacts explosively with oxygen.
🌐 The ratio of hydrogen to oxygen produced is approximately 2:1, which corresponds to the chemical formula of water, H2O.
🔄 The process of electrolysis can be reversed to combine hydrogen and oxygen back into water.
📚 Additional educational videos on hydrogen and related chemistry topics are available for further learning.

Q & A

What is electrolysis?
-Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous chemical reaction. In the context of the script, it refers to the decomposition of water into its constituent elements, hydrogen and oxygen, using electrical voltage.
What is the purpose of the Hoffmann apparatus used in the video?
-The Hoffmann apparatus is used to demonstrate the electrolysis of water. It allows for the separation of water into hydrogen and oxygen gases at the anode and cathode, respectively.
What gases are produced during the electrolysis of water?
-During the electrolysis of water, hydrogen gas is produced at the cathode (minus pole), and oxygen gas is produced at the anode (plus pole).
How does the presenter prove that hydrogen gas is produced at the cathode?
-The presenter proves that hydrogen gas is produced at the cathode by conducting a 'knallgas probe' (pop test), which is a reaction that produces a loud popping sound when hydrogen gas is ignited in the presence of oxygen.
How does the presenter demonstrate that oxygen gas is produced at the anode?
-The presenter demonstrates the production of oxygen gas at the anode by conducting a 'flammability test' (spark test) using a glowing splint. If the splint reignites more vigorously, it indicates the presence of oxygen, which supports combustion.
What is the chemical formula for water, and how does it relate to the gases produced during electrolysis?
-The chemical formula for water is H2O. During electrolysis, water is split into its elemental components: hydrogen (H2) and oxygen (O2). This is in accordance with the formula, where two hydrogen atoms combine with one oxygen atom to form water.
Why is there more hydrogen gas produced than oxygen gas during the electrolysis process?
-There is more hydrogen gas produced than oxygen because, according to the chemical formula of water (H2O), there are two hydrogen atoms for every oxygen atom. Therefore, twice as much hydrogen gas is produced compared to oxygen gas.
What is the significance of the term 'anode' in the context of electrolysis?
-In the context of electrolysis, the term 'anode' refers to the electrode where oxidation occurs. It is the positive electrode where oxygen gas is produced.
What is the significance of the term 'cathode' in the context of electrolysis?
-In the context of electrolysis, the term 'cathode' refers to the electrode where reduction occurs. It is the negative electrode where hydrogen gas is produced.
How does the presenter ensure that the gases produced are pure and not mixed with air?
-The presenter ensures the purity of the gases by using a closed system with collection tubes (hähne) in the Hoffmann apparatus, which helps to prevent the entry of air from the surroundings.
What additional information does the presenter provide about the composition of water?
-The presenter provides additional information that water is composed of hydrogen and oxygen in a 2:1 ratio, which is evident from the chemical formula H2O and the observation that twice as much hydrogen gas is produced compared to oxygen during electrolysis.

Outlines

00:00

🔬 Electrolysis of Water Experiment

The speaker begins by introducing the concept of electrolysis, explaining it as a process where a substance is split into its fundamental elements using electrical current or voltage. The focus is on the electrolysis of water, which splits it into hydrogen and oxygen. The speaker references a previous video about the production of hydrogen and oxygen from water and aims to demonstrate the same through the use of a special apparatus known as the Hoffmann decomposition apparatus. The apparatus is filled with water and has two electrodes. The speaker connects these electrodes to a power source with 20 volts of direct current. The experiment is recorded in a close-up to show the gases forming at both electrodes. The speaker notes that more gas is produced at the negative electrode than at the positive electrode and plans to test the gases to confirm their identity.

05:04

🔬 Analysis of Gases Produced During Electrolysis

The speaker continues by conducting tests to identify the gases produced at the positive and negative electrodes. Using a glowing splint test, the speaker confirms that the gas at the positive electrode (anode) is oxygen, as it reignites the glowing splint more brightly, indicating a higher concentration of oxygen. The speaker then performs a 'pop test' to identify hydrogen at the negative electrode (cathode). The test is successful, confirming the presence of hydrogen. The speaker explains that by applying a voltage of around 20 volts, water was decomposed into its constituent elements, with oxygen forming at the positive electrode and hydrogen at the negative. The speaker also discusses the stoichiometry of water, noting that water (H2O) is composed of two hydrogen atoms and one oxygen atom, which explains the observed ratio of hydrogen to oxygen gas produced during electrolysis.

10:06

😀 Wrapping Up the Experiment

In the final paragraph, the speaker concludes the video by summarizing the experiment's findings and providing additional resources for viewers interested in learning more about hydrogen. The speaker wishes the viewers a good day and encourages them to explore more chemistry videos on the channel.

Mindmap

Keywords

💡Electrolysis

Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous chemical reaction. In the context of the video, electrolysis is used to decompose water into its constituent elements, hydrogen and oxygen. The script describes how the process is carried out using a device called the 'Hoffmann decomposition apparatus', where water is subjected to an electric current of 20 volts, resulting in the production of gases at the electrodes.

💡Hydrogen

Hydrogen is a chemical element with the symbol H and atomic number 1. It is the lightest element in the periodic table and is a colorless, odorless gas. In the video, hydrogen is produced at the cathode (negative electrode) during the electrolysis of water. The script mentions that hydrogen gas is collected and tested using a 'spark test' to confirm its identity.

💡Oxygen

Oxygen is a chemical element with the symbol O and atomic number 8. It is a highly reactive nonmetal and is essential for life. In the video, oxygen is produced at the anode (positive electrode) during the electrolysis process. The script describes how the presence of oxygen is confirmed through a 'glow test' using a reagent glass.

💡Hoffmann Decomposition Apparatus

The Hoffmann decomposition apparatus is a device used to electrolyze water. It is mentioned in the script as the tool used to demonstrate the electrolysis of water. The apparatus consists of two electrodes submerged in water, through which an electric current is passed to decompose the water into hydrogen and oxygen gases.

💡Anode

The anode is the electrode through which conventional current flows into a polarized electrical device. In the video, the anode is where oxygen gas is produced during electrolysis. The script refers to the positive electrode as the anode and explains that pure oxygen is generated there.

💡Cathode

The cathode is the electrode from which conventional current flows out of a polarized electrical device. In the context of the video, the cathode is where hydrogen gas is produced during the electrolysis of water. The script describes the cathode as the negative electrode.

💡Water

Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans. In the video, water is the substance being decomposed into hydrogen and oxygen gases through electrolysis. The script explains that water is composed of hydrogen and oxygen, as demonstrated by the electrolysis process.

💡Electrical Current

Electrical current is the flow of electric charge. In the video, an electrical current of 20 volts is applied to the water in the Hoffmann decomposition apparatus to initiate the electrolysis process. The script mentions that the current causes water to split into hydrogen and oxygen gases.

💡Glow Test

The glow test is a method used to identify the presence of oxygen. In the video, a glow test is performed by introducing a glowing splint into a reagent glass containing the gas produced at the anode. The script describes how the glowing splint reignites in the presence of oxygen, confirming its production during electrolysis.

💡Spark Test

The spark test is a method used to identify the presence of hydrogen. In the video, a spark test is conducted by igniting the gas collected at the cathode. The script mentions that the test is positive, indicating the presence of hydrogen, as hydrogen gas will burn with a 'pop' sound when mixed with air.

💡Combination Reaction

A combination reaction is a chemical reaction where two or more substances combine to form a single product. In the video, the script explains that when hydrogen and oxygen are combined, they react to form water, which is the reverse of the electrolysis process demonstrated.

Highlights

Introduction to the electrolysis of water, a process where water is split into its fundamental elements through electrical current.

Explanation of the electrolysis process and the role of electrical current in breaking down water into hydrogen and oxygen.

Demonstration of the electrolysis of water using a special apparatus called the Hoffmann decomposition apparatus.

Observation of gas formation at both electrodes during the electrolysis process.

Comparison of gas volumes at the positive and negative electrodes, with less gas at the positive electrode.

Hypothesis that the gas at the positive electrode is oxygen and at the negative electrode is hydrogen.

Use of a glowing splint test to confirm the presence of oxygen at the positive electrode.

Explanation of how oxygen supports combustion, as evidenced by the glowing splint test.

Confirmation that the gas at the negative electrode is hydrogen through the use of a 'knallgas' test.

Explanation of the chemical composition of water as H2O, and the resulting gases from its electrolysis.

Observation that hydrogen gas is produced in roughly double the amount of oxygen gas during electrolysis.

Discussion on the chemical reaction of hydrogen and oxygen to form water, and the implications of the electrolysis results.

Conclusion that water is composed of hydrogen and oxygen, supported by the electrolysis experiment.

Additional resources provided for further understanding of hydrogen and related chemistry experiments.

Encouragement for viewers to explore more chemistry videos on the channel.

Final thoughts on the significance of understanding the composition of water through electrolysis.