Tag: Redox Reaction

Introduction

A battery is an electronic device that converts chemical energy to electrical energy through a redox reaction. They are typically composed of a combination of cells, with cells being the fundamental unit of batteries. Energy is stored in these cells and drawn as current and thus, the output of any battery depends on the combination of cells used inside it. 

There are two terminals on batteries, of which, one end is known as the cathode and the other end as the anode. Upon connecting a circuit to the battery, electrons can move from one node to the other and thus, current can flow through the circuit. In electrical circuits, batteries and cells can be connected in various combinations such as series, parallel, and even mixed. Today, various types of batteries are available in the market, including Pb-acid batteries, Li-ion batteries, Ni-Cd batteries, etc.

Important terms related to battery

EMF of battery: When no external factors and voltage sources are present, the potential difference between the two terminals of the battery is known as its emf, short for electromotive force.

Terminal voltage: When current starts flowing in the circuit, the potential difference between the battery’s terminals is termed as terminal voltage. Note that since the battery is an electrical device, resistance to current flow is natural. The resistance offered by the battery itself is known as internal resistance, and it creates a voltage drop across its terminals.

Let V be this voltage drop and E be the emf of the battery. Then,

Internal voltage drop= E-V

Internal resistance: As mentioned, the battery has an inherent resistance inside it, which is known as internal resistance.

Batteries in series and parallel

Series combination

This is like creating a train of batteries. The positive terminal of each battery is connected to the negative terminal of the next one and in this arrangement, the same amount of current flows through each of them. Hence, the voltages offered by the batteries can be added algebraically to get:

Parallel combination

In this combination, the positive terminals of all the batteries are connected to each other and the same is done for all the negative ones. In this configuration, the voltages dropped across the terminals remain the same and we can add current algebraically.

Connecting batteries in series

Series combination is used when we need to increase the voltage without changing the amount of current. Here is an example:

Say we had a battery of EMF 20 V and capacity 100 A-h. Then, if we connect them in series as shown below, we would end up with a combination that yielded us 40 V output but with no change in capacity.

Series combination

Hence, we get an output with increased voltage. Note that the capacities of the batteries must be the same or they might get damaged.

Advantages of Series Combination

1. Since the current flow does not increase, there is no additional heat generated.
2. It is simpler than parallel combinations.
3. The voltage drop increases.

Disadvantages of Series Combination

1. Any break or damage in the circuit at any point will damage the circuit.
2. Increased number of components also increases the resistance of the circuit.
3. A low voltage system is not compatible with this combination.

Batteries in Parallel

If we wish to increase the capacities of batteries without changing the output voltage, we use a parallel configuration. This increases the current flow in the circuit. For instance, given two batteries of 24 V, 100 A-h each, connecting them in parallel would give us a battery that provides 200 A-h at 24 V.

Parallel Combination

This sort of combination is used in solar panels.

Advantages of Parallel Combination

1. The capacity increases, yielding to increase in use-time,
2. The voltage remains the same.

Disadvantages of Parallel Combination

1. The current is increased, causing heat to increase.
2. Charging batteries in this configuration takes longer.

Mixed Combination

As implied by the name, mixed combination is the combination of some batteries connected in series linked together in parallel combination or vice versa. This is a complex arrangement that can help us generate almost any combination we want from a given bunch of batteries.

For example, suppose we were given six batteries of 15 V and 100 A-h each. We could combine them as follows:

1. Set 1 – B1 and B2 linked in series = 15V + 15V = 30V, 100 amp hour
2. Set 2 – B3 and B4 linked in series = 15V +15V = 30V, 100 amp hour
3. Set 3 – B5 and B6 linked in series = 15V + 15V = 30V, 100 amp hour

Next, we would combine the above sets in parallel, giving us a 30 V, 300 A-h configuration, visible in the diagram below.

Mixed combination

Hence, the effective voltage drop will remain at 30 V, but the capacity would be three-folds.

Summary

Depending on our requirements and the scenario in question, different combinations of batteries can be used. The most commonly used ones are series, parallel, and mixed grouping of batteries. What we use is entirely up to us and depends on the requirements of the circuit. The output of the configuration depends on its design and thus, if we needed higher voltage, we would opt for series combination and if needed higher capacity, we would use parallel configuration. Similarly, mixed grouping allows us to generate arbitrary configurations from a given set of batteries.

Frequently Asked Questions

1. Can we put a 12V 100 amp hour battery and a 15V 200 amp hour battery in a series combination?

No, since they have different capacities. For series combination, the capacities of the batteries must be the same.

2. How does a battery work?

A battery is composed of electrochemical cells, which convert chemical energy into electrical energy. When connected to a circuit, ions flow inside, leading to the flow of current.

3. Name the reaction that takes place in the batteries

The process is known as redox reaction and it involves reduction and oxidation simultaneously.

4. How are batteries classified?

Batteries may be classified as follows:

1. Primary batteries: These are one-time batteries which can not be recharged after they get depleted.
2. Secondary batteries: These batteries can be recharged after use, giving them longer life. 

5. What type of electrical combination is used for domestic purposes and why?

In domestic applications, parallel combination is used since it supplies an equal amount of voltage to all the devices, which is necessary for proper functioning.

Introduction

How does a mobile phone’s battery charge when plugged into its charger, or how does the cell in a TV remote control work? All of these questions have answers in the scientific field of electrochemistry. Electrochemistry is the study of both the use of electricity to conduct non-spontaneous chemical reactions and the production of electricity through chemical reactions. To achieve the goal, cells are used. Cells are components that initiate chemical reactions that produce or generate electricity.

What is an electrochemical reaction?

An electrochemical reaction is any process that is initiated or accompanied by the flow of electrical current, and typically involves the transport of electrons between two substances—one solid and one liquid. An electrochemical reaction occurs when a solid electrode and a material, such as an electrolyte, interact. This flow causes the reaction to release or absorb heat by producing an electric current to pass across the electrodes. When, for example, two electrodes in contact with one another initiate an oxidation and reduction (redox) reaction, the oxidation number of all the atoms involved in the reaction changes.

The process of electrochemical reaction

The properties of the negatively charged\(\;{e^ – }\)determine how matter interacts with an electric current as it flows through a system. Because protons are positively charged matter units found in elements, groups of atoms, or molecules, the electron, the fundamental unit of electricity, is drawn to them. This attraction is comparable to the chemical attraction that particles have for one another. Every chemical reaction changes the structure of an atom’s electrons, and the liberated electrons can either join with matter particles to form reductions or be ejected by them (oxidation). 

Faraday’s rules define the quantitative relationship between a free electron in a current flow and the atoms of a substance, where they cause a reaction. Electrochemical process components are also known as ionic conductors or electrolytes.

What is an Electrochemical cell?

An electrochemical cell is a system that can generate electrical energy from spontaneous chemical reactions. The chemical processes that occur during this process are known as redox reactions. During redox reactions, electrons are transferred between chemical species. They are also referred to as galvanic or voltaic cells. An electrochemical cell is illustrated by the Daniell cell.

The following are the essential components of an electrochemical cell:

1. An electrolyte is a substance found between electrodes that, when dissolved in polar solvents such as water, produces freely flowing ions, resulting in an electrically conducting solution.
2. Electrodes are solid electrical conductors that are used in electrochemical cells and are made of good conductors, such as metals.
3. They are available in two varieties:
4. The Cathode is the area of the cell where reduction takes place.
5. The anode is the part of the cell where oxidation takes place.
6. A salt bridge connects the oxidation and reduction halves of an electrochemical cell, completing the circuit. It is brimming with KCl and other saturated salt solutions. The bridge is required for the ions in the solution to flow between half-cells.

What are the different kinds of electrochemical cells?

There are two major kinds:

1. Galvanic Cell / Voltaic Cell: Chemical energy is converted to electrical energy in these electrochemical cells.
2. Electrolytic Cell: In these cells, electrical energy is converted to chemical energy.

Explain its operation

• Working Principle

The fundamental operating principle of an electrochemical system is the transfer of\(\;{e^ – }\)produced by a redox reaction occurring in it, which results in an electric current.

• Working Mechanism 

When the switch is turned on after an electrochemical cell has been fully assembled, the galvanometer of the external circuit deflects. The needle of the galvanometer moves in the direction of the beaker containing the copper sulphate solution. It indicates that the current has changed direction from the copper sulphate solution beaker to the zinc sulphate solution beaker. When the circuit is completed, a change occurs that causes zinc atoms in the zinc electrode to oxidise and Cu atoms in the copper rod to reduce. Zinc releases two electrons, which copper accepts via an external circuit.

Full redox reaction: \(\;Zn{\rm{ }}\left( s \right){\rm{ }} + {\rm{ }}C{u^{2 + }}\left( {aq} \right){\rm{ }} \to {\rm{ }}Z{n^{2 + }}\left( {aq} \right) + Cu{\rm{ }}\left( s \right)\;\;\;\)

Some applications of Electrochemical Cell

1. Many non-ferrous metals are electro-refined in metallurgy using electrolytic cells, yielding very pure metals such as Pb, Zn, Al, and Cu. 
2. It is used to recover pure Na metal from molten NaCl by storing it in an electrolytic cell.
3. Silver oxide batteries are used in hearing aids.
4. Thermal batteries are used in Navy gadgets for military applications.

Applications of Electrochemistry

1. Electrical batteries are created using the concept of cells. A battery is a device used in science and technology that stores chemical energy and provides electrical access to it.
   1. Applications in defence (thermal batteries)
   2. Digital cameras (Li batteries)
   3. Audio equipment (silver-oxide batteries)
2. Electroplating is used for a variety of purposes, including the production of jewellery and the corrosion protection of certain metals.
3. Electrochemistry is required in a variety of industries, including the chlor alkali industry.

Summary

Electrochemistry is a fascinating subject. Electrochemical reactions are important to comprehend because they have significant academic and practical implications. Understanding the responses allows us to better understand how everyday objects such as a battery or cell work. Chemical energy can be used to generate electrical energy in electrochemical cells, and electrical energy can be used to generate chemical energy.

Frequently Asked Questions 

1. What factors affect electrode potential?

Ans. The reduction potential refers to an electrode’s ability to accept electrons, whereas the oxidation potential refers to an electrode’s tendency to lose electrons. The potential of an electrode is determined by the temperature and metal ion concentration at its surface.

2. Can a zinc pot be used to store copper sulphate solution?

Ans. Copper has a lower reactivity than zinc. As a result, zinc can remove Cu from its salt solution. If the\(\;CuS{O_4}\) solution is kept in a zinc container, copper will be removed from the solution.

\[Zn + CuS{O_4} \to ZnS{O_4} + Cu\]

As a result, the copper sulphate solution cannot be stored in a zinc pot.

3. In the SI system, what is the emf measurement?

Ans. The energy contained in a battery per Coulomb of charge is known as the electromotive force, EMF has a SI unit of volts, which is equal to joules per coulomb.

Introduction

We can see the effects of oxidation and reduction reactions in daily life. This has a variety of consequences. Some of its instances, such as burning fuels, digestion of food in our bodies, and so on, are boons to humanity and highly beneficial to the continuation of life.

Do you know, in human bodies, respiration is the oxidation reaction? During this process, the food is oxidized and produces energy. On the other hand, some of its effects are highly harmful, such as air pollution from burning fuels, food rancidification, metal corrosion, etc.

Oxidation Reaction Examples

In many ways, oxidation reactions have an impact on our daily lives. While some of them are advantageous, others have unfavourable effects. The following are some typical oxidation reaction examples:

• In human bodies, respiration triggers an oxidation reaction. During respiration, food is oxidized to produce energy.
• Metal corrosion is a type of oxidation reaction.
• Fried foods acquire a bad flavour and a bad odour after being exposed to air for a long time (rancidity).
• Any substance that burns or is consumed undergoes an oxidation reaction, which always results in the production of energy. 
• Energy is produced by the combustion of various fuels in a variety of domestic and industrial processes.

Oxidation Reaction’s Effects on Daily Life

Now let us discuss oxidation reactions in everyday life. Have you ever noticed how oxidation processes affect your daily life? Maybe you have, but you’re not aware that they involve an oxidation process.  Rusting is an example of an oxidation reaction that you may be familiar with:

Rusting

A type of metal corrosion is rusting. When air and moisture in the surrounding environment interact with a metal, corrosion results. It is a result of the metal oxidizing. Because iron oxidizes in the presence of air and water to produce hydrated iron oxide, it rusts (\(F{e_2}{O_3}.x{H_2}O\)). The metal surface develops a reddish-brown layer of iron oxide.

\[4Fe{\rm{ }} + {\rm{ }}3{O_2}\, + {\rm{ }}2x{H_2}O \to F{e_2}{O_3}.x{H_2}O{\rm{ }}\left( {Rust} \right)\]

Long-term corrosion or rusting harms metal-bodied constructions. Rust develops on car bodies, bridges, railings made of iron, and ships. The metal can be kept from corroding by having paint or enamel applied to its surface.

Rancidity

The rotting of food is another typical consequence of oxidation in daily life. When foods with fats or oils are left out in the air for a long time, they begin to rancid. This is caused by the food’s fatty acids slowly oxidizing in the air, which leaves the food tasting and smelling unpleasant. The phenomenon known as “rancidity” occurs when food items are exposed to the air and undergo colour, texture, taste, and odour changes due to atmospheric oxidation.

Combustion

One of the most significant oxidation reactions is combustion. Since energy is a by-product of all combustion reactions, these processes are known as exothermic reactions because they emit heat energy.

• Energy is a necessity for our society. Any fuel that burns in the presence of air, including kerosene, petroleum, coal, wood, and charcoal, produces heat. Methane in natural gas is burned during combustion, releasing carbon dioxide and water when there is too much oxygen.
• Thermal power plants burn coal to create electricity, while natural gas is used in kitchens. We can observe how important redox reactions are to maintaining our quality of life in this way. Fuel combustion generates thermal energy, which not only powers our economy but also keeps us warm and alive. 

\[C{H_4}\, + \,2{O_2} \to C{O_2} + {\rm{ }}2{H_2}O\]

• Animals need the heat energy that they produced during food digestion. The human body also acts as a machine that burns and oxidizes all the food that is given to it to produce energy. The body gets its energy from sugar or carbohydrates like glucose (C6H12O6), fructose, and starch. When sugar and oxygen are burned, carbon dioxide, water, and heat are produced.

\[{C_6}{H_{12}}{O_6} + {\rm{ }}6{O_2} \to {\rm{ }}6C{O_2} + {\rm{ }}6{H_2}O{\rm{ }} + {\rm{ }}energy\]

 The harmful effect of combustion

Despite the many benefits of combustion, its negative impact on our life needs to be properly addressed. Fossil fuel combustion results in hazardous vapours that contain dangerous gases such as carbon monoxide, nitrogen oxides, sulphur dioxide, and sulphur trioxide. When released into the atmosphere, fumes and smoke from furnaces and car exhaust severely pollute the air. It degrades our health and does direct harm to our bodies.

Summary

In addition to harming food, oxidation also harms metals. Corrosion is the term used to describe the harmful effect of oxidation on metals, and rancidity is used to describe it on food. Thus, the corrosion of metals and the rancidity of food are two common outcomes of oxidation reactions that are seen in daily life. Aerial oxidation is another name for the oxidation that oxygen in the air causes. The prevention of rancidity, corrosion, and their effects on daily life were all covered in this article.

Frequently Asked Questions

1.What happens when something oxidizes?

Ans. The deterioration in the quality of food products, including off flavours and odours, is caused by oxidation, a chain reaction that takes place in the presence of oxygen. It depends on how the product is made, how it is packaged, how it is stored, and what ingredients are used.

2. What distinguishes burning from combustion?

Ans. Combustion is just an oxidation reaction that releases energy; burning is a type of combustion that is followed by the evolution of gas and is distinguished by flame. Burning is combustion that results in a fire, but not all combustions result in a flame.

3. How is oxygen transported to the cell, so it can keep breathing?

Ans. Humans breathe in oxygen, which travels via many alveoli in the lung (tiny air sacs). These air sacs transfer oxygen into the blood, which carries it to the cells. The oxygen from the lungs is transferred to the blood, where it connects with the red blood cell’s haemoglobin and travels to all the cells where it is discharged. The lungs receive the waste carbon dioxide from the cells and transfer it there for expiration.