thermochemical equation

(noun)

A special equation type, denoting the overall change in energy.

Related Terms

Examples of thermochemical equation in the following topics:

  • Thermochemical Equations

    • Thermochemical equations are chemical equations which include the enthalpy change of the reaction, $\Delta H_{rxn}$ .
    • A thermochemical equation is a balanced stoichiometric chemical equation which includes the enthalpy change.
    • The equation takes the form:
    • The equation takes the form:
    • Therefore, all thermochemical equations must be stoichiometrically balanced.

  • Pressure and Free Energy

    • Therefore, Gibbs free energy is most useful for thermochemical processes at constant temperature and pressure.

  • The Hydrogen Economy

    • Other methods include photoelectrocatalytic production, thermochemical production, and high temperature and pressure electrolysis.

  • The Henderson-Hasselbalch Equation

    • The equation can be derived from the formula of pKa for a weak acid or buffer.
    • The balanced equation for an acid dissociation is:
    • After taking the log of the entire equation and rearranging it, the result is:
    • The equation for the reaction is:
    • Calculate the pH of a buffer system using the Henderson-Hasselbalch equation.

  • Balancing Nuclear Equations

    • Nuclear reactions may be shown in a form similar to chemical equations, for which invariant mass, which is the mass not considering the mass defect, must balance for each side of the equation.
    • The complete equation therefore reads:
    • Therefore, the equation should read:
    • The visual representation of the equation we used as an example.
    • Describes how to write the nuclear equations for alpha and beta decay.

  • Thermodynamics of Redox Reactions

    • The thermodynamics of redox reactions can be determined using their standard reduction potentials and the Nernst equation.
    • In order to calculate thermodynamic quantities like change in Gibbs free energy $\Delta G$ for a general redox reaction, an equation called the Nernst equation must be used.
    • Walther Nernst was a German chemist and physicist who developed an equation in the early 20th century to relate reduction potential, temperature, concentration, and moles of electrons transferred.
    • If T is held constant at 298K, the Nernst equation can be condensed using the values for the constants R and F:
    • This equation allows the equilibrium constant to be calculated just from the standard reduction potential and the number of electrons transferred in the reaction.

  • Amount of Reactants and Products

    • Chemical equations are symbolic representations of chemical reactions.
    • Therefore, in a balanced equation each side of the chemical equation must have the same quantity of each element.
    • The relationship between the products and reactants in a balanced chemical equation is very important in understanding the nature of the reaction.
    • A chemical equation shows what reactants are needed to make specific products.
    • So the left side of the equation, $2\text{H}_2 + \text{O}_2$, has four hydrogen atoms and two oxygen atoms, as does the right side of the equation, $2\text{H}_2\text{O}$.

  • Molecular, Ionic, and Complete Ionic Equations

    • Precipitation reactions can be written as molecular, ionic, or complete ionic equations.
    • The resulting equation is known as the complete ionic equation, and it looks as follows:
    • In this equation, every ion is written out on both sides.
    • The equation is balanced with the molar amount of each ion preceding it.
    • This can be simplified to the net or complete ionic equation, which is shown below:

  • Balancing Redox Equations

    • Notice that this equation is balanced in both mass and charge: we have one atom of iron on each side of the equation (mass is balanced), and the net charge on each side of the equation is equal to zero (charge is balanced).
    • Add the two equations to cancel out the electrons to balance the equation.
    • We need to balance this equation by mass.
    • The equation is now balanced in mass, but not charge.
    • Notice that the final equation is balanced in mass as well as charge (each side of the equation has a net charge of +3).

  • Writing Chemical Equations

    • A chemical equation is the symbolic representation of a chemical reaction.
    • This equation would be read as "CH four plus two O two yields CO two and two H two O."
    • This equation indicates that oxygen and CH4 react to form H2O and CO2.
    • The equation also identifies that all the compounds are in the gaseous state.
    • Identify the symbols used to represent the states of matter in a chemical equation.