Chemical Energy – Talking about chemical energy seems unreal. Yet in everyday life we must find. If you are in a relationship with someone, you need “chemistry” with him , right ?
Chemistry in everyday life is defined as harmony between the two people involved. What about Chemical Energy? Is there a correlation?
Definition of Chemical Energy
So if there are atoms interacting with atoms, chemical energy will be produced.
Not much like humans, when humans meet each other, energy is generated, whether it’s a feeling that causes happiness or a feeling of sadness that makes you cry.
Chemical energy is also defined as the potential of a chemical substance to undergo a chemical reaction and then change into another substance. The form of chemical energy can only occur in energy storage devices.
Some examples of chemical energy storage media that we usually encounter include batteries, food, and gasoline.
The breaking or making of chemical bonds also involves energy, which can be absorbed or evolved from chemical systems.
Breaking bonds between atoms will produce energy, when atoms join again to form bonds also produce energy. This energy change can be estimated from the bond energies of various chemical bonds in the reactants and products.
Yes, just like us, if you break up with your boyfriend, you will usually feel sad, but some are happy.
Likewise, when you form a new bond, you can feel sad or happy. Think of it as energy!
Chemical potential energy is also a form of potential energy related to the structural arrangement of atoms or molecules. Every element or compound has potential energy because they are made up of molecules that are constantly moving or vibrating.
This arrangement may be the result of forming chemical bonds within the molecule or otherwise breaking chemical bonds. Chemical energy of a chemical substance can be converted into other forms of energy through chemical reactions
Kinds of Chemical Energy
1. Chemical Energy into Electrical Energy
There electrical energy can be converted into chemical energy and vice versa through electrochemical reactions.
The chemical reaction that can produce it is an oxidation-reduction reaction, aka redox.
Reduction and oxidation processes in which electrons are released or accepted produce electrical energy.
How come? Look , oxidation is a reaction that releases electrons. While reduction is the reaction of accepting electrons. The process of handing over the electrons will produce electrical energy.
Devices that use this concept are called voltaic cells. The Voltaic cell is called because the inventor of this device is Volta. He made a device that could generate electricity. As a source of electricity, the tool he made has 2 poles, namely the cathode as the positive pole and the anode as the negative pole. Both poles are made of 2 different metals.
Volta has measured the reduction potential or reduction ability of each metal, which is symbolized as E⁰ reduction. With different reduction capabilities, a potential difference will be generated that produces electricity
Suppose we make a voltaic cell by pairing 2 metals namely iron (Fe) and copper (Cu).
Fe has a reduced E⁰ of -0.44 volts, while Cu has a reduced E⁰ of
+0.34 volts,
Indeed, Fe and Cu have reduction potential, but when they are paired, it is impossible for both to reduce, one must give in and experience reduction.
Because the reduction ability of Fe is lower than Cu, Cu will carry out the reduction process and Fe oxidation when these two metals are paired.
It turns out that the potential energy generated is + 0.78 volts.
The resulting E⁰ cell can be obtained by the formula
E⁰cell= E⁰reduction- E⁰oxidation
= +0.34-(-0.44)
= + 0.78 Volts
This potential energy is electrical energy. This figure is generated as the potential difference of Cu and Fe metals.
Illustration of the ionic reaction between Cu and Fe
2. Chemical Energy into Heat Energy
Chemical reactions that produce heat energy are discussed in thermochemistry.
According to the law of the conservation of energy, energy cannot be created or destroyed, meaning that the energy of the universe is constant, only its form changes.
If there is energy that accompanies a chemical process, or a physical process, there is only a transfer or change in the form of energy.
So, next, we replace the energy change with the term system. Everything outside the system we call the environment.
In thermochemistry, there are two types of reactions based on the change in heat that occurs:
a. exothermic
The sum of the energy of all forms of energy possessed by molecules or particles of matter is called internal energy (E).
The energy in a substance or system can change if that system absorbs or releases heat.
If a substance or system absorbs heat, its internal energy will increase and the vibration or movement of its molecules will increase.
This increase in internal energy will cause an increase in temperature, a change in state (melting or vaporizing) or a chemical change.
An exothermic reaction occurs when a certain amount of heat is released by the system to the surroundings.
For example, in a container we have a glass and then we measure the temperature to 35⁰ C. After that we put substance Y. It turns out that after we measure the temperature rises to 45⁰ C.
In exothermic, the system releases heat so that heat increases. It is hot here, the heat of substance X will increase so that the initial H<H the end of the arrow is directed downward.
If we find the difference, then ∆H is negative
Example ½ N2(g) + 3/2 H2→NH3(g) ∆H=- 46 kJ
Reaction NH3 formation releases 46 kJ of heat energy
The analogy is like this.
For example, if person B has money, then the money is given to person A so that B so that person B has less money, while person A’s money increases. We call A is environment and B is system then money is heat.
b. Endoterm
An endothermic reaction occurs when a certain amount of heat is absorbed by the system from the environment.
Energy in a substance or system can also change if they do or receive work (external work).
It’s like us, who will expend energy if we move, but if we are lazy , aka lazy to move, not much energy can be produced.
The type of work that accompanies chemical changes or physical processes (changes in form) is expansion work, namely work related to volume changes. Work, means there is a volume that we expand or narrow.
If a substance or system expands, the substance expels air or lifts a weight above it.
To do this work, a certain amount of energy is needed, which is called work.
So, if the substance or system does work, its internal energy decreases, even though the substance or system does not release heat. Conversely, if the system receives work (the volume decreases), the system energy increases.
For an endothermic reaction, for example, in a container we have a glass, then we measure the temperature to 35⁰C. After that, we add substance X. It turns out that after we measure the temperature drops to 25⁰C.
Endoteme illustration
There is a decrease in temperature because substance X, which acts as a system, absorbs heat from the water. Water acts as an environment.
The analogy is like this.
For example, if person A has money, then person B takes the money so that person A has less money, while person B increases. We call A is environment and B is system then money is heat.
In endotherms, if the ambient temperature is detected to fall, the system takes heat energy so that the heat increases.
Heat energy here is defined as enthalpy, the heat of substance X will increase so that the initial H<the final H.
If we look for the difference, then the ∆H is positive
Example:
NH3 (g) → ½ N2(g) + 3/2 H2 (g) ∆H=+ 46 kJ
The decomposition reaction of NH3 absorbs 46 kJ of heat energy
The next energy change we call the enthalpy change or heat change. The enthalpy change that accompanies a reaction depends on the temperature and pressure gauge. The enthalpy change measured at 25 ⁰C and 1 atm pressure, is called the standard enthalpy change. The change in enthalpy is not seen from the measurement conditions, it is enough to simply state ∆H.
The equation for the reaction followed by the change in enthalpy is called a thermochemical equation. Because it is classified as an extensive property, the value of the enthalpy change written in the thermochemical equation must correspond to the stoichiometry of the reaction, meaning that the number of moles of substances involved in the reaction must be equal to the reaction coefficient.
Enthalpy Types
1. Standard enthalpy of formation
Elements react with elements to form 1 mole of compounds that can absorb or release energy. Example of enthalpy of formation
½ N2(g) + 3/2 H2→NH3(g) ∆H=- 46 kJ
So here the nitrogen element meets the oxygen element to form an ammonia compound or NH3 by releasing heat of 46 kJ. The amount of 1 mol indicated by the reaction coefficient NH3 does not exist, which means the coefficient is one
For example, the enthalpy of formation is the process of forming a marriage AB, for example person A meets person B and then they get married and become one AB. There are definitely emotions whether it’s sad or happy. Si A and B consider the elements and marriage AB as compounds. Emotions are analogous to heat energy
2. Standard enthalpy of decomposition
The opposite of a formation reaction is decomposition, so 1 mol of a compound breaks down into
Elements and elements. The decomposition reaction can absorb or release energy. Example of enthalpy of formation
NH3(g)→½ N2(g) +3/2 H2 ∆H=- 46 kJ
So here the nitrogen element meets the oxygen element to form the compound ammonia or NH3. The amount of 1 mol indicated by the reaction coefficient NH3 does not exist, which means the coefficient is one
If we take the example that the enthalpy of decomposition is a process of divorce, for example AB is divorced and separated, respectively, A and B must have emotions, whether sad or happy.
Persons A and B consider AB’s elements and marriage as compounds. Emotions are analogous to heat energy
3. Standard enthalpy of combustion
In addition to the formation and decomposition of compounds that have the potential to produce energy, combustion reactions are also capable of producing energy.
The enthalpy of combustion is defined as the heat energy produced by the combustion of 1 mole of an element or 1 mole of a compound.
Example:
enthalpy of combustion C
C (s) + ½ O2(g) →CO(g) ∆H=- 110.5 kJ
Combustion of 1 mole of carbon produces 110.5 kJ of heat energy
Enthalpy of combustion CO
C (s) + O2( g) →CO2(g) ∆H=- 393.5 kJ
Combustion of 1 mol CO (carbon monoxide produces 393.5 kJ of heat energy.
The enthalpy of combustion releases energy or is exothermic because heat is produced.
Chemical Energy Examples
There are many examples of chemical energy that we use in our daily life
1.Battery
Batteries are an example of converting chemical energy into electrical energy. We use batteries to keep the wall clock moving and a remote to use.
Even though when the remote is used, it usually disappears, aka forgetting where it is stored
The battery is an example of changing chemical energy into electrical energy.
Relatively inexpensive batteries are usually carbon-zinc galvanic cells, and there are several types, including standard and alkaline. This type is often also called a dry cell because there is no electrolyte solution, which replaces it is a semi-solid paste.
The car battery, which is used as a means of storing energy, is also used to supply the car’s electrical system, which you can learn about in the Car Battery Knowledge book .
Manganese(IV) oxide paste (MnO2) serves as the cathode which will accept electrons. Ammonium chloride (NH4Cl) and zinc chloride (ZnCl2) serve as electrolytes. The zinc on the outer layer serves as the anode.
The reaction that occurs: the anode: Zn→Zn2++ 2 e-
Zn will release 2 electrons then
the cathode: 2MnO2+ H2O + 2e-→Mn2O3+ 2OH-
Adding the two half reactions forms the main redox reaction that takes place in the carbon-zinc dry cell.
Zn + 2MnO2+ H2O→Zn2++ Mn2O3+ 2OH-This battery produces a cell potential of 1.5 volts.
2. Battery Batteries
This battery has six 2-volt cells connected in series. Lead metal is oxidized to Pb2+ ions and releases two electrons at the anode. Pb in lead(IV) oxide gains two electrons and forms Pb2+ ions at the cathode. Pb2+ ions mix with SO42- ions from sulfuric acid to form lead (II) sulfate at each electrode.
So the reaction that occurs when a lead-acid battery is used produces lead sulfate at both electrodes. PbO2+ Pb + 2H2SO4→2PbSO4+ 2H2O
lead-acid batteries are spontaneous and do not require energy input.
The reverse reaction, recharging the battery, is not spontaneous because it requires electrical input from the car. Current enters the battery and provides energy for the reaction where lead sulfate and water are converted to lead(IV) oxide, lead metal and sulfuric acid .2PbSO4+ 2H2O→PbO2+ Pb + 2H2SO4
3. Photosynthesis
Green plants convert solar energy into chemical energy (mostly oxygen) through a process known as photosynthesis.
The process of photosynthesis converts Carbon dioxide and water into glucose and oxygen. Oxygen that we really need when doing breathing or respiration
Reaction of photosynthesis:
6CO2 + 6H2O → C6H12O6 + 6O2
Photosynthetic activity occurs during the day because it requires the help of sunlight.
Try looking for trees during the day
If there is no shoulder to lean on, look for a tree to lean on .
Even though it seems like there are no activities, this one is healthier because there is a lot of oxygen that has just been released fresh from the oven
In addition to stronger trees, we will also feel fresh because a lot of oxygen has just been released by the photosynthesizing trees. With the help of a gentle breeze, drowsiness is guaranteed to strike.
Photosynthesis is an endothermic reaction because it absorbs heat.
4. Burning of fuel
The burning gasoline then produces power to run motorized vehicles. Gasoline is a type of hydrocarbon combustion reaction as follows
CxHy + O2→CO2 + H2O
The reaction of burning fuel is an exothermic reaction based on the heat released, and includes the enthalpy of combustion based on the type of reaction that occurs.
5. Digestion of food
Starting from stopping food in the mouth, sliding through the esophagus and then swimming in the stomach and in the intestines, many chemical reactions accompany it. When food is finished digesting, energy is produced to be used in activities.
For dieters, it may be commonplace to calculate how many calories you will get from a food source. In order not to overdo it, the calories needed by the body are usually counted. If it’s too much then the calories that should be used as energy will accumulate in the body to become fat deposits, right?
So actually obesity occurs when the calories used are less than the calories taken
6. Respiration / breathing
The process of breathing is a chemical reaction that produces heat. So we classify respiration as exothermic.
The reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O
There is heat generated by the breathing process
That’s the discussion of chemical energy. Hopefully with this explanation the knowledge of chemical energy will be more wide open.
Chemical energy so far has provided a myriad of benefits in our daily lives. Hopefully, after studying chemical energy, our chemistry with chemistry will get better.