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Table of Content
|1||What is Enthalpy In Physics?|
|2||Unit of Enthalpy:|
|3||Enthalpy Change Equation:|
|4||How to Calculate Enthalpy Change?|
|5||Enthalpy of Exothermic and Endothermic Reaction:|
|6||Is enthalpy a negative change in heat or positive change in heat?|
|7||What is the main cause of enthalpy?|
|8||Can we calculate absolute enthalpy?|
|9||What is the relationship of enthalpy and pressure exerted on a system?|
|10||What are the dimensions of enthalpy?|
An online enthalpy calculator is specially designed to calculate exact amount of enthalpy generated in a thermodynamic system. With the help of this tool, you can use either enthalpy formula or reaction scheme method to calculate changes in enthalpy.
So, before we move towards the brief explanation and calculation of enthalpy, let us discuss the basic phenomenon of enthalpy in the galaxy of Physics.
In the context of Physics, Enthalpy is referred to the change in heat. Addition of internal energy to the product of volume and pressure exerted on any thermodynamic system results in enthalpy. Whenever a system changes its state from solid to liquid (latent heat of fusion) or liquid to gas (latent heat of vaporization), it requires a sufficient intake of energy to produce a comprehensive change in enthalpy.
Hess’s law, Reaction Scheme and Enthalpy Formula are the most efficient ways to enumerate enthalpy of any thermodynamic system or chemical reaction. We will elaborate each of these ways in a brief manner to understand the proper concept for determining change in heat.
Did you know?
“delta h calculator helps you to determine almost absolute change in heat of any thermodynamic system.”
Examples of Enthalpy:
Real life examples of enthalpy change includes refrigerators and hand warmers. The reaction to the iron oxidation in hand warmers and vaporization of the refrigerants in compressor create a change in heat of the whole system at a constant pressure.
Standard Enthalpies of formation:
It is not possible to learn enthalpies of every substance. But for the sake of ease and time saving, we have arranged a table containing standard change in enthalpy of formation of substances that are mostly used in every chemical reaction.
|Sr # .||Name of Substance||Symbolic Formula||Standard Enthalpy of Formation ‘ΔH’|
According to System International (SI), the enthalpy is expressed in joule per kilogram or simply joule.
At a constant temperature and pressure, the enthalpy equation for a system is given as follows:
ΔH = ΔQ + p * ΔV where;
The exact values of all the parameters mentioned in enthalpy change formula above can be determined using online free enthalpy calculator.
When we calculate change in enthalpy, we can find heat change at each step during the reaction by following the thumb rule of Reaction Scheme.
For a general reaction;
anA + bnB + cnC → dnD + enE + fnF
the enthalpy equation is as follows;
“ΔH° of reaction = ∑ΔH°f(products) – ∑ΔH°f(reactants)”
With the help of online enthalpy calculator, we can easily get heat changes at each step in the reaction and overall heat, ΔHf° within a few seconds.
However, an online Heat Specific Calculator will allow you to determine the specific heat, mass of substance, initial and final energy of any substance.
We can easily calculate the enthalpy changes by taking into account each of ways mentioned above. Let us discuss the following examples to understand the concept.
Let’s suppose we have a thermodynamic system having internal energy of 5J. The pressure exerted on the system due to surroundings is 12Pa and the change in volume of the system is 39m3. What is the enthalpy of the system?
As we know that the enthalpy change formula is given as;
ΔH = ΔQ + p * ΔV
By putting the values of pressure, internal energy and change in volume, we can calculate change in enthalpy of the system as follows;
Example # 02:
Using reaction scheme, Determine change in enthalpy of the chemical reaction as follows:
2H2 + O2 → 2H2O?
Where standard enthapy of formation for each substance is given as follows:
H2=0, O2=0, H2O= -241.9
∑ΔH°f(reactants) = 2(0) + 0
∑ΔH°f(products) = 2(-241.9)
ΔH°reaction = -483.8 – 0
So, the overall change in enthalpy of reaction is -483.8kJ.
You can easily put these values in online enthalpy calculator to obtain desired result.
Let us discuss another example to determine heat of formation of the reaction using Hess’s law of heat summation.
Using Hess’s Law evaluate the enthalpy of formation, ΔHfo, of FeCl3(s) from changes in enthalpy of the following two-step process that occurs under standard state conditions:
Fe(s)+Cl2(g)⟶ FeCl2(s)ΔH°= -258.69kJ
We need to focus to find enthalpy of formation of FeCl3(s), which is equal to ΔH° for the reaction:
Fe(s)+5/2Cl2(g)⟶ FeCl3(s) ΔHfo=?
By looking at the reactions, we see that the overall enthalpy ΔHfo for FeCl3(s) is equal to the sum of two reactions with known ΔH values.
Fe(s)+Cl2(g)⟶ FeCl2(s) ΔH°= -258.69kJ
FeCl2(s)+3/2Cl2(g)⟶ FeCl3(s) ΔH°= −47.7kJ
Fe(s)+5/2Cl2(g)⟶ FeCl3(s) ΔHfo= -306.39
The enthalpy of formation, ΔHf, of FeCl3(s) is −306.39 kJ/mol.
Example # 04:
You are given the enthalpy of a system as 7J. The internal energy of the system is approximately 4.1J and the volume is 11m3. Calculate the pressure exerted on the system due to its surroundings.
as we know that:
ΔH = ΔQ + p * ΔV
by making considerable change in enthalpy equation, we get;
p = ΔH – ΔQ / ΔV
p = 7 – 4.1 / 11
p = 0.263pa
However, an online Chemical Equation Balancer Calculator will provide you the balanced equation, equilibrium constant with chemical name and formula of all reactants and product of a chemical equation.
During an exothermic reaction, the overall energy of products remains less than that of reactants. That is why heat change is always negative as the heat is released in the surroundings.
In case of endothermic reaction, enthalpy is always positive because the products are higher in energy than the reactants and reaction absorbs energy from its surroundings.
We can calculate enthalpy change easily by using two different ways in online enthalpy change calculator. These ways are;
The enthalpy calculator calculates:
The enthalpy of a reaction can either be positive or negative. Endothermic reactions result in positive enthalpy while exothermic reactions give rise to negative enthalpy.
Changes in heat during product formation in a chemical reaction is a major cause of enthalpy generation.
No, we can’t calculate the absolute enthalpy as reaction schemes take place at every temperature and thus change in heat occurs at all times which changes the enthalpy of the system continuously.
There exists a direct relationship among enthalpy and pressure. Increasing pressure on a system causes an increase in enthalpy of the system and vice versa.
As enthalpy is a state function, it has the dimensions of energy and thus measured in ergs or jouls.
Enthalpy is a heat content of a thermodynamic system or chemical reaction. The enthalpy is never determined by its history and depends upon temperature, pressure and change in surroundings. When it comes to change in heat, boiler engineers typically use an enthalpy calculator online to decrease the uncertainty of calculations.
From the source of Wikipedia: Characteristic functions, Physical interpretation, Relationship to heat, Heat of reaction, Specific enthalpy, Throttling, Compressors.
From the source of Libre Text: Enthalpy Change Accompanying a Change in State, Effect of Temperature on Enthalpy, The Enthalpy of Phase Transition.
From the source of Lumen Learning: Internal Energy and Enthalpy, Internal Energy Change at Constant Volume, Standard Enthalpy of Reaction, Enthalpy of Reaction at Constant Pressure, Exothermic and Endothermic Processes, Exothermic Reactions.