AI Tools
Health
Math
Everyday Life
Finance
Physics
Chemistry
Statistics
Construction
Pets
Time & Date
Conversion Calculator
Sign InPages
Category
Follow Us On:
Pages
Category
Follow Us On:
Enter the values to calculate the enthalpy change using the formula or chemical reaction scheme.
Add this calculator to your site
This enthalpy calculator calculates the enthalpy change (ΔH) involved in a process along with the initial and final enthalpy values using Hess's Law or standard enthalpies of formation. It provides valuable insights into chemical reactions to help you analyze energy variations and understand the thermodynamics of the system.
Enthalpy measures the total energy released or absorbed in a thermodynamic system. It is the sum of the total internal energy and the product of pressure and volume.
Whenever a system changes its state from solid to liquid or liquid to gas, it requires sufficient energy intake. It is called the latent heat of fusion or vaporization, respectively. The latent heat of fusion and vaporization are specific examples of enthalpy changes associated with phase transitions.
Enthalpy = H = U + PV
Where:
According to System International (SI), the enthalpy is expressed in joules (J) or kilojoules (kJ). As it's not possible to directly calculate the total enthalpy of a chemical reaction, the change in enthalpy is calculated. This change indicates the amount of heat absorbed or released during the reaction. There are two types of reactions:
ΔH = ΔQ + p * ΔV
Where:
anA + bnB + cnC → dnD + enE + fnF
The formula for standard enthalpy of formation is given below:
“ΔH° of reaction = ∑ΔH°f(products) - ∑ΔH°f(reactants)”
Where:
Suppose a chemical reaction occurs at a constant pressure of 45 Pascals. The reactants possess an internal energy of 55 Joules and obtain a volume of 65 cubic meters. Now system transitions to a state where the products exhibit an internal energy of 45 Joules and occupy a volume of 35 cubic meters. Calculate the initial, final enthalpies, and the enthalpy change.
Solution:
Given that:
Let's find Δ U:
Δ U = U(products) - U_(reactants) = 45 j - 55 j = -10 j
Now calculate ΔV:
Δ V = V(products) - Vreactants = 35 m3 - 65 m3 = - 30 m3
Find P ΔV:
P ΔV = 45 Pa x (-30 m3) = -1350 j
Finally, find delta h:
Δ H = Δ U + P ΔV = -10 j + (-1350 j) = -1360 J
The change in enthalpy of reaction is:
Δ H = -1360 j
Initial enthalpy (H(initial)):
For the reactants:
H(initial) = Ureactants + P Vreactants = 55 j + 45 Pa x 65 m3
Calculate the term (P V(reactants)):
P V(reactants = 45 Pa x 65 m3 = 2925 j
So,
H(initial) = 55 j + 2925 j = 2980 j
Final enthalpy (H(final)):
For the products:
H(final) = U(products) + P V(products) = 45 j + 45 Pa x 35 m3
Calculate the term PVproducts):
PVproducts) = 45 Pa x 35 m3 = 1575 j
So, the final enthalpy is:
H(final) = 45 j + 1575 j = 1620 j
After performing the calculation we get - 1360 j as enthalpy change. This negative sign indicates that it's an exothermic reaction. The calculations become even easier with the use of an online enthalpy calculator because it provides you with the step-by-step calculation of enthalpy change.
|
Sr No. |
Name of Substance |
Symbolic Formula |
Standard Enthalpy of Formation ‘ΔH’ |
|
1. |
Potassium Chloride |
KCl(s) |
-435.9 |
|
2. |
Potassium Chlorate |
KClO3(s) |
-391.4 |
|
3. |
Sodium Chloride |
NaCl(s) |
-411.0 |
|
4. |
Sodium Hydroxide |
NaOH(s) |
-426.7 |
|
5. |
Zinc Sulphide |
ZnS(s) |
-202.9 |
|
6. |
Zinc Oxide |
ZnO(s) |
-348.0 |
|
7. |
Copper Sulphate |
CuSO4(s) |
-769.9 |
|
8. |
Copper Oxide |
CuO(s) |
-155.2 |
|
9. |
Calcium Dioxide |
Ca(OH)2(s) |
-986.6 |
|
10. |
Water |
H2O(l) |
-285.8 |
|
11. |
Chloroform |
CHCl3(l) |
-131.8 |
|
12. |
Carbon Dioxide |
CO2(g) |
-393.5 |
|
13. |
Hydrogen Sulphide |
H2S(g) |
-20.1 |
|
14. |
Ammonia |
NH3(g) |
-46.2 |
|
15. |
Sulphur Trioxide |
So3(g) |
-395.2 |
|
16. |
Hydrochloric Acid |
HCl(g) |
-92.3 |
|
17. |
Nitrogen Oxide |
NO(g) |
+90.4 |
|
18. |
Nitrogen Dioxide |
NO2(g) |
+33.9 |
|
19. |
Phosphorus Pentachloride |
PCl5(g) |
-398.9 |
|
20. |
Phosphorus Trichloride |
PCl3(g) |
-306.4 |
|
21. |
Sulphur Dioxide |
SO2(g) |
-296.1 |
The Hess law states, "No matter whether the reaction happens in one step or multiple steps, the energy released or absorbed during the chemical reaction is the same”.
Determining the enthalpy is important for various reasons including:
Liquids have higher enthalpy as compared to the solids because of:
Yes, it can be calculated but it's complex because the interaction of substances with different components can affect the enthalpy
References:
From the source of Wikipedia: Enthalpy.
Add this calculator to your site.
×Just copy a given code & paste it right now into your website HTML (source) for suitable page.
Preview:
Give Us Your Feedback
Share Result
Enthalpy Calculator
Links
Home Conversion Calculator About Calculator Online Blog Hire Us Knowledge Base Sitemap Sitemap TwoSupport
Calculator Online Team Privacy Policy Terms of Service Content Disclaimer Advertise TestimonialsEmail us at
[email protected]© Copyrights 2025 by Calculator-Online.net