Electrolysis of Water & Hydrochloric Acid | Reactions | Chemistry | FuseSchool

FuseSchool - Global Education
21 Apr 202004:07
EducationalLearning
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TLDRThis script explores the fundamentals of electrolysis, a process named by Michael Faraday, who also coined terms like 'anode' and 'cathode.' It explains how adding sulfuric acid to water enhances electrolysis without changing the products, which are hydrogen and oxygen gases, collected in a 2:1 ratio. The script delves into the redox reactions occurring at the electrodes, with oxygen forming at the anode through oxidation and hydrogen at the cathode through reduction. It also notes that acidifying water with hydrochloric acid alters the reaction, producing chlorine gas at the anode. Safety precautions with chlorine's toxicity are highlighted.

Takeaways
  • 🔋 The discovery of splitting water using electric current happened soon after the discovery of current electricity.
  • 🧪 Michael Faraday introduced most of the terms used in electrolysis today.
  • 🔍 Electrolysis means using electricity to split something apart, a term coined by Faraday.
  • ⚡ The electrolysis cell consists of a positive anode and a negative cathode.
  • 💧 Pure water is a poor conductor of electricity because it barely ionizes at room temperature.
  • 🧴 Adding sulfuric acid to water improves its ability to undergo electrolysis without changing the products.
  • 🌊 Electrolysis produces gas bubbles at both electrodes, more at the cathode.
  • ⚙️ Using a Hofmann voltammeter, gases from electrolysis can be collected in a 2:1 ratio.
  • 🔄 The balanced equation of electrolysis gives gases in a two-to-one ratio, hydrogen to oxygen.
  • 🔋 In redox reactions during electrolysis, oxygen forms at the anode and hydrogen forms at the cathode.
Q & A
  • Who discovered that passing an electric current through water would split it apart?

    -The discovery was made quite soon after the discovery of current electricity itself, predating Michael Faraday's work in this area.

  • Who introduced most of the terms used in electrolysis today?

    -Michael Faraday introduced most of the terms used in electrolysis.

  • What does the term 'electrolysis' mean, and who named it?

    -Electrolysis means using electricity to split something apart, and it was named by Michael Faraday.

  • What equipment is used in electrolysis and who named most of it?

    -The equipment includes a cell with a positive anode and a negative cathode, electrodes connected to the cell, and the liquid being electrolyzed, called the electrolyte. Most of this equipment was named by Faraday.

  • Why is pure water a poor conductor of electricity?

    -Pure water is a poor conductor of electricity because it is a covalent molecule that hardly ionizes at room temperature, resulting in a very small concentration of free ions needed to carry current.

  • How can the ability of water to undergo electrolysis be increased without altering the products obtained?

    -By adding a little sulfuric acid to water, the ability of water to undergo electrolysis is greatly increased without altering the products obtained.

  • What gases are produced during the electrolysis of water, and in what ratio?

    -During the electrolysis of water, bubbles form around both electrodes, with more around the cathode. The gases produced are in a ratio of two to one.

  • What are the ions present in water and what do they do during electrolysis?

    -The ions present in water are the hydrogen ion and the hydroxide ion. These ions are attracted to the electrode with the opposite charge during electrolysis.

  • What reactions occur at the anode and cathode during the electrolysis of water?

    -At the anode, oxygen is made through a loss of electrons, which is an oxidation reaction. At the cathode, hydrogen is made by gaining electrons, which is a reduction reaction.

  • How does acidifying water with hydrochloric acid alter the electrolysis reaction?

    -When water is acidified with hydrochloric acid, the presence of chloride ions alters the reaction, resulting in the oxidation of chloride anions and the production of chlorine gas at the anode instead of oxygen.

  • Why must precautions be taken when working with chlorine in the lab during electrolysis?

    -Precautions must be taken because chlorine is toxic and very soluble in water, requiring care to avoid exposure.

Outlines
00:00
🔬 The Discovery and Terminology of Electrolysis

This paragraph delves into the early discovery of passing an electric current through water to split it apart, predating Michael Faraday's work. Faraday, however, introduced most of the terminology we use today, including the term 'electrolysis,' which means using electricity to split something apart. The paragraph explains the basic equipment used in electrolysis, named by Faraday: a cell with a positive anode and a negative cathode, electrodes, and the electrolyte. Pure water, being a poor conductor due to its covalent nature, requires sulfuric acid to enhance its electrolyzing ability. The paragraph concludes by describing the formation of bubbles around both electrodes and the collection of gases in a two-to-one ratio using a Hofmann voltammeter.

💧 Ion Behavior and Redox Reactions in Electrolysis

This paragraph provides a detailed look at the ions present in water—hydrogen ions and hydroxide ions—and their attraction to electrodes with opposite charges. It explains Faraday's terminology of 'anions' (ions that go to the anode) and 'cations' (ions that go to the cathode). At the anode, oxygen is produced through an oxidation reaction, while at the cathode, hydrogen is produced via a reduction reaction, leading to an overall redox reaction. The paragraph highlights the two-to-one ratio of gases formed and introduces the mnemonic 'oil-rig' (Oxidation Is Loss, Reduction Is Gain) to track electrons in redox reactions.

⚗️ Effects of Hydrochloric Acid on Electrolysis

This paragraph discusses how acidifying water with hydrochloric acid alters the electrolysis reaction due to the presence of chloride ions (Cl-). Instead of hydroxide ions, chloride anions are oxidized, producing chlorine gas at the anode instead of oxygen. The reaction remains a redox reaction, but the gases are produced in equal amounts. The paragraph notes that chlorine's higher solubility in water compared to hydrogen means it takes longer to observe appreciable amounts of chlorine gas. It ends with a safety reminder about chlorine's toxicity and the importance of taking precautions when working with it in a lab setting.

Mindmap
Keywords
💡Electrolysis
Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction. In the context of the video, it refers to the splitting of water into hydrogen and oxygen gases. The script highlights that electrolysis was named by Michael Faraday, who also introduced many of the terms used in the process, such as 'anode' and 'cathode'. The script explains that electrolysis of pure water is inefficient due to the lack of free ions, but the addition of substances like sulfuric acid increases the conductivity and facilitates the process.
💡Michael Faraday
Michael Faraday was a renowned English scientist known for his contributions to the field of electromagnetism and electrochemistry. The script mentions Faraday as the person who introduced most of the terms used in electrolysis, such as 'electrolysis' itself, 'anode', 'cathode', and 'electrolyte'. His work laid the foundation for understanding the principles of using electricity to split substances.
💡Anode
An anode is the electrode through which conventional current flows into a polarized electrical device. In the script, it is explained that during electrolysis, the anode is the positive electrode where oxidation occurs, such as the production of oxygen gas when water is electrolyzed.
💡Cathode
A cathode is the electrode from which conventional current flows out of a polarized electrical device. The script describes the cathode as the negative electrode where reduction takes place, such as the formation of hydrogen gas during the electrolysis of water.
💡Electrolyte
An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The script notes that the liquid being electrolyzed, such as water with added sulfuric acid, acts as the electrolyte, providing the ions necessary for the conduction of electricity during electrolysis.
💡Ion
An ion is an atom or molecule that has a net electrical charge due to the loss or gain of one or more electrons. The script explains that ions, specifically hydrogen ions and hydroxide ions, are necessary for the conduction of electricity in the electrolyte during electrolysis.
💡Covalent Molecule
A covalent molecule is a type of chemical bond formed by the sharing of electron pairs between atoms. The script mentions that water is a covalent molecule, which at room temperature does not ionize easily, resulting in a very low concentration of ions and making pure water a poor conductor of electricity.
💡Oxidation
Oxidation is a chemical process in which a substance loses electrons. In the script, oxidation is described as occurring at the anode during electrolysis, where oxygen is produced as electrons are lost to the anode.
💡Reduction
Reduction is a chemical process in which a substance gains electrons. The script explains that reduction occurs at the cathode during electrolysis, where hydrogen gas is formed as electrons are gained from the cathode.
💡Redox Reaction
A redox reaction, short for reduction-oxidation reaction, involves the transfer of electrons between two species. The script describes the simultaneous occurrence of oxidation at the anode and reduction at the cathode during electrolysis, combining to form a redox reaction.
💡Hofmann Voltammeter
A Hofmann voltammeter is a type of apparatus used to study the electrolysis of solutions and to collect gases produced at the electrodes. The script mentions its use to collect and identify the gases produced during the electrolysis of water.
💡Acidification
Acidification is the process of increasing the acidity of a solution, often by adding an acid. The script explains that acidifying water with hydrochloric acid alters the electrolysis reaction, leading to the production of chlorine gas at the anode instead of oxygen due to the presence of chloride ions.
Highlights

The discovery that passing an electric current through water would split apart was made soon after the discovery of current electricity.

Michael Faraday introduced most of the terms used in electrolysis today.

Faraday named electrolysis, which means to use electricity to split something apart.

Electrolysis equipment includes a cell with a positive anode and a negative cathode.

Pure water is a poor conductor of electricity due to its low ionization at room temperature.

Adding sulfuric acid to water increases its ability to undergo electrolysis without changing the products.

Bubbles form around both electrodes during electrolysis, with more around the cathode.

Using a Hofmann voltammeter, gases produced can be collected and are made in a ratio of two to one.

The initial solubility of oxygen in water sometimes masks the two to one gas ratio.

Hydrogen ions and hydroxide ions in water are attracted to electrodes with opposite charges.

Faraday called the ions moving to the anode anions and those to the cathode cations.

Oxygen is produced at the anode, which is an oxidation reaction, while hydrogen is produced at the cathode, a reduction reaction.

The overall reaction is a redox reaction, producing gases in a two to one ratio.

If water is acidified with hydrochloric acid, chloride ions are oxidized, producing chlorine instead of oxygen at the anode.

Chlorine gas is more soluble in water than hydrogen, delaying its visibility in the experiment.

Chlorine is toxic, requiring precautions when working with it in the lab.

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