Advanced thermodynamic engine with professional chemical formula parser and automatic species cancellation.
This calculator uses a Stoichiometric String Engine. To ensure perfect results, follow these input patterns:
-> to separate reactants and products.2H2O). Fractions like 1/2 are supported.-3.93e2) and exponents (10^2).(s), (l), (g), (aq) are recognized and treated as distinct species.CH4 + 2O2 -> CO2 + 2H2O | ΔH: -890.3
Fundamental pillars of the law:
Crucial for reactions that are:
Definition: The total enthalpy change for a chemical reaction is the same regardless of whether the reaction occurs in one step or several steps.
Target: 3C(s) + 4H2(g) → C3H8(g)
In thermodynamics, Δ represents a change in a state function. For Enthalpy (ΔH), it is defined as Hproducts - Hreactants. Because absolute enthalpy cannot be measured directly, we measure the heat flow during the transition.
Yes. Since ΔS and ΔG are also State Functions, they obey the additive property of Hess's Law. Research in chemical engineering uses this summation method to predict if a reaction will happen spontaneously without needing dangerous laboratory tests.
The Law of Conservation of Mass states that atoms cannot be created or destroyed. If your input has 3 Carbons on the left side but only 1 on the right, the math will be invalid. You must ensure every atom is accounted for in your coefficients.
Our smartParser supports standard notation. You can enter 10^3 for 1000 or -5.6e-2 for -0.056. This is especially useful for lattice energy research where energy values are extremely high.
If your target equation needs 3 moles of a substance but your reference reaction only provides 1, enter 3 in the multiplier. The engine multiplies both the molecules and the ΔH value, following the extensive property of enthalpy.
Yes. Based on the First Law of Thermodynamics, if a forward reaction releases heat (exothermic), the reverse must absorb heat (endothermic). Toggling this switch automatically multiplies your ΔH value by -1.
Enthalpy depends on the physical state. For example, forming H2O(l) releases -285.8 kJ, but forming H2O(g) releases only -241.8 kJ. The difference is the heat of vaporization. Always include these to ensure accuracy.
Yes. In professional thermochemistry, fractional coefficients are used to represent the formation of exactly one mole of a product. You can type 1/2 or 0.5 into any numeric field.
The parser identifies groups like SO4 or PO4. It breaks them into individual atoms (Sulfur, Oxygen, etc.) and cross-references them against our 118-element database to verify atomic balance.
Proposed by Germain Hess in 1840, this law was a major breakthrough before the Law of Conservation of Energy was fully understood. Today, it is the foundation for Computational Chemistry used in drug discovery.
Most standard data is measured at 25°C (298.15 K). If your steps occur at different temperatures, you would need Kirchhoff's Law. This solver assumes a constant temperature for all steps.
A positive (+) final ΔH means the system absorbed heat. In industrial manufacturing, these reactions require constant heating from an external source to stay active.
This maintains Significant Figures. Most high-precision calorimeters are accurate to 0.01 kJ. Rounding prevents "false precision" where the numbers look more accurate than the actual lab equipment allows.
It is the most stable form of an element at 1 bar of pressure. For instance, Oxygen is a gas (O2) and Carbon is Graphite. This is why the enthalpy of formation for pure elements in these states is always 0.
Yes. The engine uses a recursive stack. It looks at the "2" outside the parenthesis and automatically knows there are 2 Oxygens and 2 Hydrogens, ensuring your balancing check is 100% correct.
The layout uses Modern CSS Grid. On a phone, the input boxes and FAQ items will automatically stack vertically to ensure you can calculate on the go without zooming in.