Thermochemistry is the Application of the First Law of Thermodynamics
Thermochemistry is the application of the first law of thermodynamics to chemical events that discuss the heat that accompanies chemical reactions.
Thermochemistry can be defined as a part of chemistry that studies the dynamics or changes in chemical reactions by observing only the heat / thermals. One of the applications of this knowledge in daily life is the chemical reaction in our body where the production of the energies needed or expended for all the tasks we do. Combustion from fuels such as oil and coal are used for electricity generation.
Gasoline that is burned in a car's engine will produce power that causes the car to run. If we have a gas stove it means we burn methane gas (the main component of natural gas) which produces heat for cooking. And through a sequence of reactions called metabolism, the food eaten will produce the energy we need for the body to function. Almost all chemical reactions there is always energy taken or expelled.
With studies conducted on the application of thermochemistry in everyday life. And to outline the problem in more detail, the author tries to make a paper whose contents discuss the "Application of Thermochemistry in Everyday Life".
Thermochemical Equations
Is a reaction equation that includes the enthalal change (DH).
The DH value written in the thermochemical equation, adjusted for the stoichiometry of the reaction, means = the number of moles of a substance involved in a chemical reaction = the reaction coefficient; (the reactant phase and the reaction product must be written).
Problems example :
In the formation of 1 mole of water from hydrogen gas with oxygen at 298 K, 1 atmosphere is released at 285.5 kJ.
The thermochemical equation:
If the coefficient is multiplied by 2, then the price of the reaction DH must also be multiplied by 2.
Some things that must be considered in writing the thermochemical equation:
The reaction coefficient shows the number of moles of the substance involved in the reaction.
When the reaction equation is reversed (changing the reactant's location with the product), the DH value remains the same but the sign is opposite.
If we multiply both sides of the thermochemical equation by the y factor, the DH value must also be multiplied by the y factor.
When writing the thermochemical reaction equation, the reactant phase and the product must be written down.
Energy Changes in Chemical Reactions
Almost in every chemical reaction there will always be absorption and release of energy. If chemical changes occur in the bulkhead container, so there is no heat entering or leaving the system. Thus the total energy possessed by the system is fixed. There are two energy changes in a chemical reaction: endothermic changes and exothermic changes. Endorterm changes are changes that are able to flow heat from the system to the environment or release heat into the environment
When exothermic changes occur as the temperature of the system increases, the potential energy of the substances involved in the reaction decreases. While the exothermic change is the heat that will flow into the system. If an endothermic change occurs, the temperature of the system decreases, the potential energy of the substances involved in the reaction will increase.
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Standard Form and Standard Decomposition Enthalpy
Standard Form and Standard Decomposition Enthalpy
The enthalpy (H) of a substance is determined by the amount of energy and all forms of energy possessed by a substance whose amount cannot be measured. Changes in heat or enthalpy that occur during the process of receiving or releasing heat are expressed as "change in enthalpy (ΔH)". For example in the change of ice into water, it can be written as follows:
Δ H = H H20 (l) -H H20 (s)
If we observe the reaction of combustion of gasoline in the engine motor. Some of the chemical energy contained in gasoline, when gasoline burns, is converted to heat energy and mechanical energy to drive the motor. Likewise with the mechanism of action of battery cells. When the battery cell is working, chemical energy is converted into electrical energy, the heat energy used to burn gasoline and the combustion reaction of gasoline produces gas, moving the piston so that the motor wheel moves.
The actual enthalpy of a substance cannot be determined or measured. But ΔH can be determined by measuring the amount of heat absorbed by the system. For example in the change of ice into water, which is 89 calories / gram. At the change of ice into water, ΔH is positive, because the enthalpy of change results, the enthalpy of water is greater than the enthalpy of ice.
Thermochemistry is a part of chemistry that studies the enthalpy changes that accompany a reaction. In chemical changes there is always a change in enthalpy. The magnitude of the change in enthalpy is as large as the difference between the enthalpy of the reaction product and the amount of enthalpy of the reactant.
In endothermic reactions, the enthalpy after the reaction becomes larger, so ΔH is positive. Whereas in exothermic reactions, the enthalpy after the reaction becomes smaller, so ΔH is negative. The change in enthalpy in a reaction is called the reaction heat. The reaction heat for typical reactions is also called a unique name, for example heat of formation, heat of decomposition, heat of combustion, heat of dissolution and so on.
Standard Form Enthalpy (piH◦f)
The standard enthalpy of formation of a compound states the amount of heat needed or freed for the process of forming 1 mole of a compound from its elements which is stable under standard conditions (STP). The enthalpy of standard formation is given the symbol (ΔH◦f), the symbol f is derived from the word formation which means formation. Examples of elements that are stable under standard conditions, namely: H2, O2, C, N2, Ag, Cl2, Br2, S, Na, Ca, and Hg.
Standard Decomposition Enthalpy (ΔH◦d)
The standard decomposition enthalpy of a compound states the amount of heat needed or freed for the process of decomposing 1 mole of a compound from its elements that are stable under standard conditions (STP). The standard decomposition enthalpy is given the symbol (ΔH◦d) d symbol derived from the word decomposition which means decomposition.
According to Laplace's Law, the amount of heat released in the formation of compounds from its elements is the same as the amount of heat needed in the decomposition of these compounds into its elements. So, the decomposition enthalpy is the opposite of the enthalpy of formation of the same compound. Thus the number of heat is the same but the sign is opposite because the reaction is in the opposite direction.
The enthalpy (H) of a substance is determined by the amount of energy and all forms of energy possessed by a substance whose amount cannot be measured. Changes in heat or enthalpy that occur during the process of receiving or releasing heat are expressed as "change in enthalpy (ΔH)". For example in the change of ice into water, it can be written as follows:
Δ H = H H20 (l) -H H20 (s)
If we observe the reaction of combustion of gasoline in the engine motor. Some of the chemical energy contained in gasoline, when gasoline burns, is converted to heat energy and mechanical energy to drive the motor. Likewise with the mechanism of action of battery cells. When the battery cell is working, chemical energy is converted into electrical energy, the heat energy used to burn gasoline and the combustion reaction of gasoline produces gas, moving the piston so that the motor wheel moves.
The actual enthalpy of a substance cannot be determined or measured. But ΔH can be determined by measuring the amount of heat absorbed by the system. For example in the change of ice into water, which is 89 calories / gram. At the change of ice into water, ΔH is positive, because the enthalpy of change results, the enthalpy of water is greater than the enthalpy of ice.
Thermochemistry is a part of chemistry that studies the enthalpy changes that accompany a reaction. In chemical changes there is always a change in enthalpy. The magnitude of the change in enthalpy is as large as the difference between the enthalpy of the reaction product and the amount of enthalpy of the reactant.
In endothermic reactions, the enthalpy after the reaction becomes larger, so ΔH is positive. Whereas in exothermic reactions, the enthalpy after the reaction becomes smaller, so ΔH is negative. The change in enthalpy in a reaction is called the reaction heat. The reaction heat for typical reactions is also called a unique name, for example heat of formation, heat of decomposition, heat of combustion, heat of dissolution and so on.
Standard Form Enthalpy (piH◦f)
The standard enthalpy of formation of a compound states the amount of heat needed or freed for the process of forming 1 mole of a compound from its elements which is stable under standard conditions (STP). The enthalpy of standard formation is given the symbol (ΔH◦f), the symbol f is derived from the word formation which means formation. Examples of elements that are stable under standard conditions, namely: H2, O2, C, N2, Ag, Cl2, Br2, S, Na, Ca, and Hg.
Standard Decomposition Enthalpy (ΔH◦d)
The standard decomposition enthalpy of a compound states the amount of heat needed or freed for the process of decomposing 1 mole of a compound from its elements that are stable under standard conditions (STP). The standard decomposition enthalpy is given the symbol (ΔH◦d) d symbol derived from the word decomposition which means decomposition.
According to Laplace's Law, the amount of heat released in the formation of compounds from its elements is the same as the amount of heat needed in the decomposition of these compounds into its elements. So, the decomposition enthalpy is the opposite of the enthalpy of formation of the same compound. Thus the number of heat is the same but the sign is opposite because the reaction is in the opposite direction.
Heat Capacity and Specific Heat
Heat Capacity and Specific Heat
The heat capacity (C) is the amount of heat needed to increase the temperature of a material sample by 1 Co. Mathematically expressed with the following equation:
DQ = C DT
Specific heat (s) is the amount of heat required to raise the temperature of 1 gram of material mass by 1 Co. If we know the specific heat and amount of a substance, the change in temperature of the substance () can express the amount of heat (q) absorbed or released in a chemical reaction.
Information:
q = heat released or absorbed (J)
= temperature change (end - beginning) (0C)
The relationship between heat capacity and heat type is formulated as follows:
Information:
C = heat capacity (J / 0C)
m = sample mass (gr)
c = heat type (J / g0C)
Enthalpy
Enthalpy (H) is the total amount of all forms of energy. The enthalpy (H) of a substance is determined by the amount of energy and all forms of energy possessed by a substance whose amount cannot be measured and will remain constant as long as no energy enters or exits the substance. Kinetic energy is generated because of the atoms and molecules of matter in randomly moving substances. The total amount of all forms of energy is called enthalpy (H). Enthalpy will remain constant as long as there is no energy entering or leaving the substance. For example enthalpy for water can be written H H20 (l) and for ice written H H20 (s).
To express the heat of a reaction at constant pressure (qp) a quantity called Enthalpy (H) is used.
H = E + (P.V)
DH = DE + (P. DV)
DH = (q + w) + (P. DV)
DH = qp - (P. DV) + (P. DV)
DH = qp
For chemical reactions:
DH = Hp - Hr
HP = enthalpy of product
Hr = reactant enthalpy
Reaction at constant pressure: qp = DH (enthalpy change)
Reaction at fixed volume: qv = DE (change in energy in)
Changes in heat or enthalpy that occur during the process of receiving or releasing heat are expressed as "change in enthalpy (ΔH)". The actual enthalpy of a substance cannot be determined or measured. But ΔH can be determined by measuring the amount of heat absorbed by the system. For example in the change of ice into water, which is 89 calories / gram.
At the change of ice into water, ΔH is positive, because the enthalpy of change results, the enthalpy of water is greater than the enthalpy of ice. In chemical changes there is always a change in enthalpy. The magnitude of the change in enthalpy is as large as the difference between the enthalpy of the reaction product and the amount of reactant enthalpy.
Every system or substance has energy stored in it. Potential energy is related to the form of matter, volume, and pressure. Kinetic energy is generated because atoms and molecules in substances move randomly. The total amount of all forms of energy is called enthalpy (H). Enthalpy will remain constant as long as there is no energy entering or leaving the substance. . For example enthalpy for water can be written H H20 (l) and for ice written H H20 (s).
The heat capacity (C) is the amount of heat needed to increase the temperature of a material sample by 1 Co. Mathematically expressed with the following equation:
DQ = C DT
Specific heat (s) is the amount of heat required to raise the temperature of 1 gram of material mass by 1 Co. If we know the specific heat and amount of a substance, the change in temperature of the substance () can express the amount of heat (q) absorbed or released in a chemical reaction.
Information:
q = heat released or absorbed (J)
= temperature change (end - beginning) (0C)
The relationship between heat capacity and heat type is formulated as follows:
Information:
C = heat capacity (J / 0C)
m = sample mass (gr)
c = heat type (J / g0C)
Enthalpy
Enthalpy (H) is the total amount of all forms of energy. The enthalpy (H) of a substance is determined by the amount of energy and all forms of energy possessed by a substance whose amount cannot be measured and will remain constant as long as no energy enters or exits the substance. Kinetic energy is generated because of the atoms and molecules of matter in randomly moving substances. The total amount of all forms of energy is called enthalpy (H). Enthalpy will remain constant as long as there is no energy entering or leaving the substance. For example enthalpy for water can be written H H20 (l) and for ice written H H20 (s).
To express the heat of a reaction at constant pressure (qp) a quantity called Enthalpy (H) is used.
H = E + (P.V)
DH = DE + (P. DV)
DH = (q + w) + (P. DV)
DH = qp - (P. DV) + (P. DV)
DH = qp
For chemical reactions:
DH = Hp - Hr
HP = enthalpy of product
Hr = reactant enthalpy
Reaction at constant pressure: qp = DH (enthalpy change)
Reaction at fixed volume: qv = DE (change in energy in)
Changes in heat or enthalpy that occur during the process of receiving or releasing heat are expressed as "change in enthalpy (ΔH)". The actual enthalpy of a substance cannot be determined or measured. But ΔH can be determined by measuring the amount of heat absorbed by the system. For example in the change of ice into water, which is 89 calories / gram.
At the change of ice into water, ΔH is positive, because the enthalpy of change results, the enthalpy of water is greater than the enthalpy of ice. In chemical changes there is always a change in enthalpy. The magnitude of the change in enthalpy is as large as the difference between the enthalpy of the reaction product and the amount of reactant enthalpy.
Every system or substance has energy stored in it. Potential energy is related to the form of matter, volume, and pressure. Kinetic energy is generated because atoms and molecules in substances move randomly. The total amount of all forms of energy is called enthalpy (H). Enthalpy will remain constant as long as there is no energy entering or leaving the substance. . For example enthalpy for water can be written H H20 (l) and for ice written H H20 (s).
Definition of Covalent Bonds According to Experts
Definition of Covalent Bonds According to Experts
A covalent bond is a bond that occurs due to the use of two electron pairs together by two atoms (James E. Brady, 1990). A covalent bond is formed between two atoms that both want to capture electrons (fellow non-metal atoms).
The electron pairs used together are called bonding electron pairs (PEI) and valence electron pairs that are not involved in the formation of covalent bonds are called free electron pairs (PEB). Covalent bonds generally occur between atoms of non-metallic elements, can be of the same type (for example: H2, N2, O2, Cl2, F2, Br2, I2) and different types (for example: H2O, CO2, etc.). Compounds that only contain covalent bonds are called covalent compounds.
Example of a Kovalen Bond
Covalent Chemical Compound Formula
By referring to the octet rule, we can predict the molecular formula of covalent-bound compounds. In this case, the number of electrons paired must be equalized. However, keep in mind that the octet rule is not always obeyed, there are some covalent compounds that violate the octet rule.
An example is the bond between H and O in H2O. Electron configuration H and O is H requires 1 electron and O requires 2 electrons. In order for O and H atoms to follow the octet rule, the number of H atoms given must be two, while O atoms are one, so the compound molecular formula is H2O.
bonding electron pairs
KOVALEN BOND TYPE
Based on the formation
A single covalent bond
A single covalent bond is a covalent bond that has 1 pair of PEI.
Example: H2, H2O (electron configuration H = 1; O = 2, 6).
Examples of bond formation in H2O molecules below:
A single covalent bond
A single covalent bond
Double covalent bond
A double covalent bond is a covalent bond that has 2 pairs of PEI.
Example: O2, CO2 (electron configuration O = 2, 6; C = 2, 4).
Here follows the formation of the 2-fold bonds in the CO2 molecule.
Double covalent bond
Double covalent bond
Triple covalent bond
A 3 covalent bond is a covalent bond that has 3 pairs of PEI.
Example: N2 (Electron configuration N = 2, 5).
The following is the formation of 3-fold bonds in the N2 molecule
Triple covalent bond
Based on Polarization:
Polar Covalent Bonds
Polar covalent bonds are covalent bonds in which the PEI tends to be attracted to one of the bonded atoms. The polarity of a covalent bond is determined by the electronegativity of an element. Polar covalent compounds usually occur between atoms of different elements with large electronegativity, having asymmetric molecular shapes, having dipole moments. Covalent bonds that occur between two different atoms are called polar covalent bonds. Polar covalent bonds can also occur between the same two atoms but have different electronegativity.
Examples of polar covalent bonds: HF
Examples of HF polar covalent bonds
In this HF compound, F has a high electronegativity compared to H ... so that the electron pair is more attracted towards F, as a result, dipoles are formed or polarity occurs (polar formation between H and F).
Nonpolar Covalent Bonds
Nonpolar covalent bonding is a covalent bond whose PEI is attracted equally to the bonding atoms. Nonpolar covalent compounds are formed between the atoms of elements that have zero electronegativity difference or have a dipole moment = 0 (zero) or have molecular symmetry. The negative charge points of the alliance electrons coincide, so that the molecules forming them do not occur dipole moments, in other words that the electron electrons get the same attraction.
Examples of Nonpolar H2 Covalent Bonds
Nonpolar covalent bonds consist of:
Kovalen Coordination Association
Coordination covalent bonds are covalent bonds in which the shared electron pair is donated by only one atom, while the other atom does not donate electrons. So here there is one atom giving a free electron pair, while another atom is the recipient. Co-ordinated covalent bonds are sometimes expressed by arrows (→) which show the direction of donation of electron pairs.
A covalent bond is a bond that occurs due to the use of two electron pairs together by two atoms (James E. Brady, 1990). A covalent bond is formed between two atoms that both want to capture electrons (fellow non-metal atoms).
The electron pairs used together are called bonding electron pairs (PEI) and valence electron pairs that are not involved in the formation of covalent bonds are called free electron pairs (PEB). Covalent bonds generally occur between atoms of non-metallic elements, can be of the same type (for example: H2, N2, O2, Cl2, F2, Br2, I2) and different types (for example: H2O, CO2, etc.). Compounds that only contain covalent bonds are called covalent compounds.
Example of a Kovalen Bond
Covalent Chemical Compound Formula
By referring to the octet rule, we can predict the molecular formula of covalent-bound compounds. In this case, the number of electrons paired must be equalized. However, keep in mind that the octet rule is not always obeyed, there are some covalent compounds that violate the octet rule.
An example is the bond between H and O in H2O. Electron configuration H and O is H requires 1 electron and O requires 2 electrons. In order for O and H atoms to follow the octet rule, the number of H atoms given must be two, while O atoms are one, so the compound molecular formula is H2O.
bonding electron pairs
KOVALEN BOND TYPE
Based on the formation
A single covalent bond
A single covalent bond is a covalent bond that has 1 pair of PEI.
Example: H2, H2O (electron configuration H = 1; O = 2, 6).
Examples of bond formation in H2O molecules below:
A single covalent bond
A single covalent bond
Double covalent bond
A double covalent bond is a covalent bond that has 2 pairs of PEI.
Example: O2, CO2 (electron configuration O = 2, 6; C = 2, 4).
Here follows the formation of the 2-fold bonds in the CO2 molecule.
Double covalent bond
Double covalent bond
Triple covalent bond
A 3 covalent bond is a covalent bond that has 3 pairs of PEI.
Example: N2 (Electron configuration N = 2, 5).
The following is the formation of 3-fold bonds in the N2 molecule
Triple covalent bond
Based on Polarization:
Polar Covalent Bonds
Polar covalent bonds are covalent bonds in which the PEI tends to be attracted to one of the bonded atoms. The polarity of a covalent bond is determined by the electronegativity of an element. Polar covalent compounds usually occur between atoms of different elements with large electronegativity, having asymmetric molecular shapes, having dipole moments. Covalent bonds that occur between two different atoms are called polar covalent bonds. Polar covalent bonds can also occur between the same two atoms but have different electronegativity.
Examples of polar covalent bonds: HF
Examples of HF polar covalent bonds
In this HF compound, F has a high electronegativity compared to H ... so that the electron pair is more attracted towards F, as a result, dipoles are formed or polarity occurs (polar formation between H and F).
Nonpolar Covalent Bonds
Nonpolar covalent bonding is a covalent bond whose PEI is attracted equally to the bonding atoms. Nonpolar covalent compounds are formed between the atoms of elements that have zero electronegativity difference or have a dipole moment = 0 (zero) or have molecular symmetry. The negative charge points of the alliance electrons coincide, so that the molecules forming them do not occur dipole moments, in other words that the electron electrons get the same attraction.
Examples of Nonpolar H2 Covalent Bonds
Nonpolar covalent bonds consist of:
Kovalen Coordination Association
Coordination covalent bonds are covalent bonds in which the shared electron pair is donated by only one atom, while the other atom does not donate electrons. So here there is one atom giving a free electron pair, while another atom is the recipient. Co-ordinated covalent bonds are sometimes expressed by arrows (→) which show the direction of donation of electron pairs.
Examples of Coordination Covalent Bonds: BF3NH3
Examples of Coordination Covalent Bonds: BF3NH3
5B = 1s2 2s2 2p1
9F = 1s2 2s2 2p5
7N = 1s2 2s2 2p3
Example of the BF3NH3 Coordination Agreement
Properties of Covalent Compounds:
Boiling point
In general, covalent compounds have a low boiling point (average below 200 0C). For example Water, H2O is a covalent compound. The covalent bonds that bind between hydrogen atoms and oxygen atoms in water molecules are quite strong, while the binding force between water molecules is quite weak. This condition causes the water in the liquid phase (form) will easily turn into water vapor when heated to around 100 0C, but at this temperature the covalent bonds in the H2O molecule do not break.
Boiling point
Volatility (ability to evaporate)
Most covalent compounds are volatile liquids and gases. The molecules in covalent compounds which have volatile properties often produce a characteristic odor. Perfume and scent ingredients are covalent compounds, for example from volatile covalent compounds
Volatility
Solubility
In general, covalent compounds can not dissolve in water, but easily dissolve in organic solvents. Organic solvents are carbon compounds, for example gasoline, kerosene, alcohol, and acetone. But there are some covalent compounds that can dissolve in water because they react with water (hydration) and form ions. For example, sulfuric acid when dissolved in water will form hydrogen ions and sulfate ions. Covalent compounds that can dissolve in water hereinafter referred to as polar covalent compounds, while covalent compounds that are not soluble in water are subsequently referred to as non-polar covalent compounds.
Solubility
Electrical conductivity
In general, covalent compounds in various forms cannot conduct electric current or are non-electrolyte, except polar covalent compounds. This is due to polar covalent compounds containing ions when dissolved in water and these compounds include weak electrolyte compounds. Here follows a picture of the difference between non-electrolyte compounds, weak electrolytes and strong electrolytes.
Thermochemistry is the science of changing heat (heat) of a substance that involves chemical and physical processes. Thermochemistry, which is part of Thermodynamics, discusses the energy changes that accompany a chemical reaction that is manifested as a reaction heat. The constituent particles are always in constant motion, so the substances have kinetic energy. The average kinetic energy of an object is directly proportional to its absolute temperature (0K).
this means that if an object is hot, the atoms of the molecules making up the object move fast, so the kinetic energy of the object is large. The potential energy of a substance arises from the attractive and repulsive forces between the constituent particles of matter. One form of energy that is commonly found is heat energy.
Heat is a form of energy that can be exchanged between the system and the environment. Reaction heat is a change in energy in a chemical reaction in the form of heat. In general, to detect the heat that is owned by an object by measuring the temperature of the object. If the temperature is high, the heat contained by objects is very large, and vice versa if the temperature is low, the heat contained is small.
A tool to measure the heat of a reaction from a chemical reaction is a calorimeter. A calorimeter that uses the technique of mixing two substances in a container, is generally used to determine the specific heat of a substance. There are two types of calorimeter namely fixed volume calorimeter and fixed pressure calorimeter.
5B = 1s2 2s2 2p1
9F = 1s2 2s2 2p5
7N = 1s2 2s2 2p3
Example of the BF3NH3 Coordination Agreement
Properties of Covalent Compounds:
Boiling point
In general, covalent compounds have a low boiling point (average below 200 0C). For example Water, H2O is a covalent compound. The covalent bonds that bind between hydrogen atoms and oxygen atoms in water molecules are quite strong, while the binding force between water molecules is quite weak. This condition causes the water in the liquid phase (form) will easily turn into water vapor when heated to around 100 0C, but at this temperature the covalent bonds in the H2O molecule do not break.
Boiling point
Volatility (ability to evaporate)
Most covalent compounds are volatile liquids and gases. The molecules in covalent compounds which have volatile properties often produce a characteristic odor. Perfume and scent ingredients are covalent compounds, for example from volatile covalent compounds
Volatility
Solubility
In general, covalent compounds can not dissolve in water, but easily dissolve in organic solvents. Organic solvents are carbon compounds, for example gasoline, kerosene, alcohol, and acetone. But there are some covalent compounds that can dissolve in water because they react with water (hydration) and form ions. For example, sulfuric acid when dissolved in water will form hydrogen ions and sulfate ions. Covalent compounds that can dissolve in water hereinafter referred to as polar covalent compounds, while covalent compounds that are not soluble in water are subsequently referred to as non-polar covalent compounds.
Solubility
Electrical conductivity
In general, covalent compounds in various forms cannot conduct electric current or are non-electrolyte, except polar covalent compounds. This is due to polar covalent compounds containing ions when dissolved in water and these compounds include weak electrolyte compounds. Here follows a picture of the difference between non-electrolyte compounds, weak electrolytes and strong electrolytes.
Thermochemistry is the science of changing heat (heat) of a substance that involves chemical and physical processes. Thermochemistry, which is part of Thermodynamics, discusses the energy changes that accompany a chemical reaction that is manifested as a reaction heat. The constituent particles are always in constant motion, so the substances have kinetic energy. The average kinetic energy of an object is directly proportional to its absolute temperature (0K).
this means that if an object is hot, the atoms of the molecules making up the object move fast, so the kinetic energy of the object is large. The potential energy of a substance arises from the attractive and repulsive forces between the constituent particles of matter. One form of energy that is commonly found is heat energy.
Heat is a form of energy that can be exchanged between the system and the environment. Reaction heat is a change in energy in a chemical reaction in the form of heat. In general, to detect the heat that is owned by an object by measuring the temperature of the object. If the temperature is high, the heat contained by objects is very large, and vice versa if the temperature is low, the heat contained is small.
A tool to measure the heat of a reaction from a chemical reaction is a calorimeter. A calorimeter that uses the technique of mixing two substances in a container, is generally used to determine the specific heat of a substance. There are two types of calorimeter namely fixed volume calorimeter and fixed pressure calorimeter.
Definition and Properties of Metal Bonds
Definition and Properties of Metal Bonds
Do you know what is meant by metal bonding ??? Because on this occasion we will discuss about the understanding of metal bonds, the characteristics of metal bonds, the nature of metal bonds, the process of forming metal bonds, and the complete example. Therefore, let us consider the review below.
Metal Bonds
Understanding Metal Bonds
Metal bonds are chemical bonds formed by the sharing of valence electron electrons between metal tomatoes. Example: ferrous metal, zinc, and silver. Metal bonds are not ionic or covalent bonds. One theory put forward to explain metal bonds is the theory of a sea of electrons. Examples of metal bonding. The place of valence electron position of an iron atom (Fe) can overlap with the place of position of the valence electron of other Fe atoms.
This overlap between valence electrons allows the valence electrons of each Fe atom to move freely in the space between Fe + ions to form a sea of electrons. Because the charges are opposite (Fe2 + and 2 e–), there is a pull between the Fe + ions and these free electrons. As a result, bonds are called metal bonds.
Characteristics of Metal Bonds
Metal atoms can be likened to ping-pong balls that are packed tightly together.
Metal atoms have very few valence electrons, so it is very easy to be released and form positive ions.
Therefore the outer shell of a metal atom is relatively loose (there are many empty spots) so that electrons can move from 1 atom to another atom.
The mobility of electrons in the metal is so free, that the metal valence electrons undergo a delocalisation, a state in which the valence electrons are not fixed on 1 atom, but always move from 1 atom to another.
The valence electrons blend into a cloud of electrons which surrounds the positive metal ions.
The presence of metal bonds causes metals to be:
Metals are solid at standard temperatures and pressures, with the exception of the element mercury and gallium which are both liquid. As a reminder, the properties of metals are as follows:
High thermal and electrical conductivity.
Sparkling and reflecting light.
Can be forged.
Have variations in mechanical strength.
Keep in mind that metal bonding is a major force that holds metal atoms together. Metal bonding is the result of the attraction of a positive charge from the metal and the negative charge of the electrons that move freely.
Metal properties cannot be included in bonding criteria such as covalent bonds or ionic bonds. Ionic compounds cannot conduct electricity in the solid phase, and ionic compounds are fragile (as opposed to metal properties). and; Atoms of metal compounds contain only one to three valence electrons. Thus the atom cannot form covalent bonds. Covalent compounds are poor conductors of electricity and are generally liquid (with the opposite properties of metal formation). Thus, the metal forms a different bonding model.
Metal Bond Formation Process
In the metal bonding process there is mutual lending of electrons, only the number of atoms together lend their valence electrons (electrons in the outer shell) not only between two but several atoms but in an unlimited number. Each atom surrenders valence electrons to be used together, thus there will be bonds of attraction between atoms that are close together.
The distance between these atoms will remain the same, meaning that if there are atoms moving away the attractive force will pull it back to its original position and if it moves too close there will be a repulsive force because the nuclei are too close when the electric charge is the same so that the position atom relative to other atoms will remain.
In metal bonds, the nuclei of a particular atom are spaced apart and arranged irregularly while electrons are lent to one another as if forming an electron mist. In metals, the outer atomic orbitals filled with electrons fuse into a delocalized system which is the basis for the formation of metal bonds. Delocalisation is a state in which the valence electrons do not remain in one atom's position, but always move from one atom to another.
Metal atoms can be joined together to connect in all directions to become a very large molecule. One atom will bind to several other atoms around it. As a result these atoms are strongly bonded and become solid (except Hg) metals and are generally hard.
Do you know what is meant by metal bonding ??? Because on this occasion we will discuss about the understanding of metal bonds, the characteristics of metal bonds, the nature of metal bonds, the process of forming metal bonds, and the complete example. Therefore, let us consider the review below.
Metal Bonds
Understanding Metal Bonds
Metal bonds are chemical bonds formed by the sharing of valence electron electrons between metal tomatoes. Example: ferrous metal, zinc, and silver. Metal bonds are not ionic or covalent bonds. One theory put forward to explain metal bonds is the theory of a sea of electrons. Examples of metal bonding. The place of valence electron position of an iron atom (Fe) can overlap with the place of position of the valence electron of other Fe atoms.
This overlap between valence electrons allows the valence electrons of each Fe atom to move freely in the space between Fe + ions to form a sea of electrons. Because the charges are opposite (Fe2 + and 2 e–), there is a pull between the Fe + ions and these free electrons. As a result, bonds are called metal bonds.
Characteristics of Metal Bonds
Metal atoms can be likened to ping-pong balls that are packed tightly together.
Metal atoms have very few valence electrons, so it is very easy to be released and form positive ions.
Therefore the outer shell of a metal atom is relatively loose (there are many empty spots) so that electrons can move from 1 atom to another atom.
The mobility of electrons in the metal is so free, that the metal valence electrons undergo a delocalisation, a state in which the valence electrons are not fixed on 1 atom, but always move from 1 atom to another.
The valence electrons blend into a cloud of electrons which surrounds the positive metal ions.
The presence of metal bonds causes metals to be:
Metals are solid at standard temperatures and pressures, with the exception of the element mercury and gallium which are both liquid. As a reminder, the properties of metals are as follows:
High thermal and electrical conductivity.
Sparkling and reflecting light.
Can be forged.
Have variations in mechanical strength.
Keep in mind that metal bonding is a major force that holds metal atoms together. Metal bonding is the result of the attraction of a positive charge from the metal and the negative charge of the electrons that move freely.
Metal properties cannot be included in bonding criteria such as covalent bonds or ionic bonds. Ionic compounds cannot conduct electricity in the solid phase, and ionic compounds are fragile (as opposed to metal properties). and; Atoms of metal compounds contain only one to three valence electrons. Thus the atom cannot form covalent bonds. Covalent compounds are poor conductors of electricity and are generally liquid (with the opposite properties of metal formation). Thus, the metal forms a different bonding model.
Metal Bond Formation Process
In the metal bonding process there is mutual lending of electrons, only the number of atoms together lend their valence electrons (electrons in the outer shell) not only between two but several atoms but in an unlimited number. Each atom surrenders valence electrons to be used together, thus there will be bonds of attraction between atoms that are close together.
The distance between these atoms will remain the same, meaning that if there are atoms moving away the attractive force will pull it back to its original position and if it moves too close there will be a repulsive force because the nuclei are too close when the electric charge is the same so that the position atom relative to other atoms will remain.
In metal bonds, the nuclei of a particular atom are spaced apart and arranged irregularly while electrons are lent to one another as if forming an electron mist. In metals, the outer atomic orbitals filled with electrons fuse into a delocalized system which is the basis for the formation of metal bonds. Delocalisation is a state in which the valence electrons do not remain in one atom's position, but always move from one atom to another.
Metal atoms can be joined together to connect in all directions to become a very large molecule. One atom will bind to several other atoms around it. As a result these atoms are strongly bonded and become solid (except Hg) metals and are generally hard.
Comparison of Physical Properties of Metal Compounds with Non-Metallic Compounds
Comparison of Physical Properties of Metal Compounds with Non-Metallic Compounds
Examples of metal bonds:
Non-Metallic Metal
1. Metal solids are good conductors of electricity 1. Non-metallic solids are usually not conductors of electricity
2. Having metal luster 2. Not shiny
3. Strong and hard (when used as an alloy metal) 3. Most non-metals are not strong and soft
4. Can be bent and stretched 4. Usually fragile and broken when bent or stretched
5. Good heat conductor 5. Difficult to deliver heat
6. Most metals have a large density 6. Most non metals have a low density
7. Most metals have a high boiling point and melting point 7. Most non-metals have a low boiling point and melting point
METAL COMPOUND REACTIONS:
Alkali metals have several physical properties including soft, shiny white and easily cut. If the metals are left open, the surface will become dull because they react easily with water or oxygen, and are usually stored in kerosene.
As the atomic number increases, the softness level also increases. The level of softness of the alkali metals increases with the increasing atomic number of the metals. The chemical properties of alkaline earth metals can be observed among other things from their reaction to water. The reaction with water produces hydrogen and hydroxide gas and is quite hot. Reactivity to cold water gets bigger with increasing metal numbers.
Alkaline earth metals, except for beryllium, are all white, easily cut and appear to be more shiny when cut, and quickly become dull in the air. Its reactivity to water varies. Beryllium can react with water in an incandescent state and the water is in the form of steam. Magnesium reacts with cold water slowly and faster when it gets hotter, other alkaline earth metals react very quickly with cold water to produce hydrogen and hydroxide gas and produce a lot of heat.
Chloride compounds from alkali metals and alkaline earth dissolve in water to form simple hydrate ions. many covalent or somewhat covalent chlorides undergo hydrolysis and produce chlorides and oxides or hydroxides. For example aluminum chloride solution reacts with water to form aluminum hydroxide.
Based on known octet rules, the hydrogen atom lacks 1 electron and the chlorine atom needs 1 electron to form a stable configuration of the noble gas group. When viewed in terms of electronegativity, chlorine has an electronegativity value that is not small. A stable configuration can be achieved by using shared electrons. The hydrogen atom and the chlorine atom each contribute one electron to form a shared pair of electrons.
In the Lewis structure for NaCl and HCl, the Cl atom obtains an electron configuration of noble gas atoms. The tendency of Cl atoms to accept an electron under any circumstances is always the same, but when compared between Na or H atoms, the atoms will not simply release their electrons. To release valence electrons from Na, energy (I1) of -5.14 eV / atom is required which is smaller than the energy needed to release valence electrons from H, which is 13.6 eV / atom. Sodium is more metallic than hydrogen. In fact, hydrogen is not a metal under normal conditions; hydrogen does not give its electrons to other non-metal atoms. The formation of a bond between an H atom and a Cl atom involves the sharing of electrons which results in a covalent bond.
Examples of metal bonds:
Non-Metallic Metal
1. Metal solids are good conductors of electricity 1. Non-metallic solids are usually not conductors of electricity
2. Having metal luster 2. Not shiny
3. Strong and hard (when used as an alloy metal) 3. Most non-metals are not strong and soft
4. Can be bent and stretched 4. Usually fragile and broken when bent or stretched
5. Good heat conductor 5. Difficult to deliver heat
6. Most metals have a large density 6. Most non metals have a low density
7. Most metals have a high boiling point and melting point 7. Most non-metals have a low boiling point and melting point
METAL COMPOUND REACTIONS:
Alkali metals have several physical properties including soft, shiny white and easily cut. If the metals are left open, the surface will become dull because they react easily with water or oxygen, and are usually stored in kerosene.
As the atomic number increases, the softness level also increases. The level of softness of the alkali metals increases with the increasing atomic number of the metals. The chemical properties of alkaline earth metals can be observed among other things from their reaction to water. The reaction with water produces hydrogen and hydroxide gas and is quite hot. Reactivity to cold water gets bigger with increasing metal numbers.
Alkaline earth metals, except for beryllium, are all white, easily cut and appear to be more shiny when cut, and quickly become dull in the air. Its reactivity to water varies. Beryllium can react with water in an incandescent state and the water is in the form of steam. Magnesium reacts with cold water slowly and faster when it gets hotter, other alkaline earth metals react very quickly with cold water to produce hydrogen and hydroxide gas and produce a lot of heat.
Chloride compounds from alkali metals and alkaline earth dissolve in water to form simple hydrate ions. many covalent or somewhat covalent chlorides undergo hydrolysis and produce chlorides and oxides or hydroxides. For example aluminum chloride solution reacts with water to form aluminum hydroxide.
Based on known octet rules, the hydrogen atom lacks 1 electron and the chlorine atom needs 1 electron to form a stable configuration of the noble gas group. When viewed in terms of electronegativity, chlorine has an electronegativity value that is not small. A stable configuration can be achieved by using shared electrons. The hydrogen atom and the chlorine atom each contribute one electron to form a shared pair of electrons.
In the Lewis structure for NaCl and HCl, the Cl atom obtains an electron configuration of noble gas atoms. The tendency of Cl atoms to accept an electron under any circumstances is always the same, but when compared between Na or H atoms, the atoms will not simply release their electrons. To release valence electrons from Na, energy (I1) of -5.14 eV / atom is required which is smaller than the energy needed to release valence electrons from H, which is 13.6 eV / atom. Sodium is more metallic than hydrogen. In fact, hydrogen is not a metal under normal conditions; hydrogen does not give its electrons to other non-metal atoms. The formation of a bond between an H atom and a Cl atom involves the sharing of electrons which results in a covalent bond.
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