Oxidation States and Electrolytic Cells

The oxidation number of an element in its elemental form is zero.

The oxidation number of a single-element ion is equal to the charge of the ion.

The oxidation number of hydrogen is typically +1 in compounds. However, it is -1 in metal hydrides.

The element with a higher electronegativity is assigned a negative oxidation number.

The sum of oxidation numbers for all atoms in a neutral molecule equals zero. The sum of oxidation numbers in an ion equals the charge of the ion.

A chemical process where an atom or molecule loses electrons and its oxidation state increases.

A chemical process where an atom or molecule gains electrons and its oxidation state decreases.

A chemical reaction where oxidation and reduction occur simultaneously.

A substance that gains electrons from another substance in a redox reaction.

A substance that loses electrons to another substance in a redox reaction.

Substances that do not form ions when dissolved in water and therefore do not conduct electricity.

An electrochemical cell where electricity drives a non-spontaneous chemical reaction.

The process by which an electric current decomposes a compound into its elements.

The electrode in an electrolytic cell where oxidation occurs, connected to the positive terminal of the power source.

The electrode in an electrolytic cell where reduction occurs, connected to the negative terminal of the power source.

Sodium chloride (NaCl) is melted and then electrolyzed to produce sodium metal and chlorine gas.

The process by which molten NaCl is broken down into its elements by applying an electric current.

The negative chlorine ions (Cl⁻) lose electrons at the anode, becoming chlorine gas (Cl₂).

The positive sodium ions (Na⁺) gain electrons at the cathode, forming liquid sodium metal (Na).

A method for producing sodium hydroxide (NaOH) using a process of electrolysis with a specific cell design.

The oxidation state of zinc in its reaction with hydrochloric acid. The reaction involves the transfer of electrons, resulting in a change in the oxidation state of zinc.

In the reaction of zinc with hydrochloric acid, the hydrogen ions (H+) from the acid gain electrons and are reduced to hydrogen gas (H2).

In the reaction 2H₂ + O₂ → 2H₂O, oxygen goes from a neutral state (0) to a negative state (-2) because it gains electrons from hydrogen to form water. It is reduced.

Zinc chloride (ZnCl₂) is the product formed when zinc reacts with hydrochloric acid. This reaction is a single displacement reaction where zinc displaces hydrogen from hydrochloric acid.

The chlorine ions (Cl-) remain unchanged in oxidation state during the zinc and hydrochloric acid reaction. They do not participate in the electron transfer process.

The oxidation number of an element in its elemental form or free state is always 0. This is because the element has neither gained nor lost electrons.

Hydrogen in metal hydrides has an oxidation state of -1. This occurs because hydrogen is more electronegative than the metal, so it attracts the shared electrons.

Oxygen in peroxides has an oxidation state of -1. This is due to the peroxide bond (O-O) where each oxygen atom shares only one electron with the other oxygen atom.

Group 2 elements (alkaline earth metals) typically have an oxidation state of +2. They tend to lose two electrons to achieve a stable noble gas configuration.

In a neutral molecule, the algebraic sum of all the oxidation numbers of the atoms must equal zero. This ensures the molecule is electrically neutral.

Non-electrolytes are substances that do not ionize in solution and therefore do not conduct electricity. They remain as neutral molecules and cannot carry electrical charge.

The main process occurring in an electrolytic cell is electrolysis, which is the chemical decomposition of a substance using an electric current. Electrolysis is the opposite of a galvanic cell.

An electrolytic cell is a device designed to carry out electrolysis. Typically, it consists of an electrolyte solution (containing ions) and two electrodes, which serve as the interfaces for the electrical current to enter the system.

A graphite rod placed in the anode compartment of Nelson's cell. It serves as the positive electrode where oxidation occurs.

A perforated iron sheet located at the bottom of the cell. It acts as the negative electrode where reduction occurs.

A porous barrier that separates the anode and cathode compartments in Nelson's cell. It restricts the flow of ions while allowing the passage of ions.

Sodium ions (Na+) in the cell, remaining in solution and combining with hydroxide ions (OH-) formed at the cathode to form sodium hydroxide (NaOH).

Electrolysis of molten sodium chloride (NaCl) in a Downs cell produces sodium metal and chlorine gas. Sodium ions (Na+) migrate to the cathode, where they gain electrons and are reduced to sodium metal (Na). Chloride ions (Cl-) migrate to the anode, where they lose electrons and are oxidized to chlorine gas (Cl2).

The process of separating brine into its constituent elements (sodium hydroxide, hydrogen, and chlorine) via electrolysis. This process involves a steel tank with a central graphite anode and a U-shaped iron cathode lined with asbestos. The brine (NaCl solution) is the electrolyte.

The electrode where reduction occurs, leading to the gain of electrons. In a Downs cell, the cathode is where sodium ions (Na+) gain electrons to become sodium metal.

The electrode where oxidation occurs, leading to the loss of electrons. In a Downs cell, the anode is where chloride ions (Cl-) lose electrons to become chlorine gas.

A porous barrier separating the anode and cathode in an electrolytic cell, like Nelson's cell. It prevents the mixing of products but allows ion flow. In Nelson's cell, it's made of asbestos.

The process of iron corroding due to a chemical reaction with oxygen and water.

This region is characterized by a higher concentration of oxygen, where electrons are gained.

Preventing rusting by removing any stains on the metal surface.

Applying a protective layer of grease or paint to stop air and moisture from reaching the metal surface.

Creating mixtures of metals to improve resistance to rusting. Stainless steel is an example.

Coating iron with a layer of zinc to prevent rusting. This is done by dipping iron in molten zinc.

A process where a thin layer of zinc is applied to iron to protect it from corrosion, even if the coating is damaged.

Electroplating is a method of depositing a thin layer of one metal onto another using electrolysis. It's like painting a metal object with another metal using electricity!

The object to be electroplated acts as the cathode (negative electrode) and attracts positively charged metal ions from the electrolyte solution. These ions are then deposited on the object, forming a thin layer of the desired metal.

The anode (positive electrode) is made of the metal being deposited. As the current flows, metal atoms from the anode lose electrons and become positive ions, which then migrate to the cathode.

Electroplating is used to protect metals from corrosion and to improve their appearance. Imagine a shiny chrome car or a silver-plated spoon. These are examples of objects that have been electroplated.

Electroplating is like a mini-factory for creating metal coatings. An electric current provides the energy to move metal ions from the anode to the cathode, where they are deposited as a thin layer, improving the object's properties.

Electroplating is a process of depositing a thin layer of metal onto another object using an electric current. It is used to protect, enhance or alter the appearance of the object.

In electroplating of zinc, the target metal acts as the cathode and is immersed in a zinc sulfate electrolyte bath. By applying an electric current, zinc ions from the solution deposit onto the target metal, coating it with zinc.

In electroplating of tin, the steel object acts as the cathode and is immersed in a tin salt solution. When an electric current is passed through the circuit, tin ions from the solution deposit onto the steel, creating a tin coating.

Electrolytic refining is a process that uses electrolysis to purify copper. Impure copper acts as the anode and a pure copper plate acts as the cathode, immersed in a copper sulfate solution. The electric current drives the process, where copper ions from the impure copper deposit onto the pure copper plate.

In electrolytic refining of copper, the process of oxidation occurs at the anode, where copper atoms lose electrons and dissolve into the solution as copper ions. The opposite process, reduction, occurs at the cathode where copper ions gain electrons and deposit as pure copper.