chemical reaction thermodynamics calculator

The units for equation (1) are now consistent: Then one mole of reaction is said to have occurred. So in our reaction, if two moles of CO react with one mole of O 2 to produce two moles of CO 2, For a chemical reaction, the change in moles for each species is tied to mol rxn by the stoichiometric coefficient. Similarly, for O 2 the coefficient would be written 2,3.

In our example the coefficient for CO would become where mol rxn refers to the reaction as written. In order to define a mole of reaction the chemical equation must be known. One mole of reaction (mol rxn) refers to a reaction unit. The stoichiometric coefficients can be thought of as representing the number of moles of a species participating in a chemical reaction per mole of reaction.

If the delta symbol were changed to reflect this intensive character, perhaps some of the misunderstanding could be alleviated, but it is unlikely that a symbol change will ever be effected. 2 In fact, all thermodynamic quantities calculated for chemical reactions, enthalpy, Gibbs energy, and entropy must have units that show the intensive property of each of the parameters i.e., units that should be on a per mole basis. In part the problem is that the stoichiometric coefficients of the equation are not recognized as being unitless. The origin of the difficulty is that the symbol as used in equation (1) refers to an intensive quantity not an extensive quantity therefore the units of must be energy/mol. Some point out that the units for should be J/mol but don't say why, some change the units of R, and some ignore the discrepancy. Different texts treat this dilemma in different ways. Now we use eqn (1): and notice that the units don't match. 1 Let us return to the original calculation of. However, at this point it is generally, but not always, recognized that there is a problem.

Several pages later, conveniently separated from the calculation of, the student is asked to calculate the equilibrium constant for the reaction from. The procedure outlined for the calculation is: Thus, the standard Gibbs energy of formation for CO is -137 kJ per mole of CO. These and other standard formation parameters refer to the formation of the compound of interest in its standard state from the elements in their standard states. Most introductory chemistry texts include an example of a calculation for the Gibbs energy change of a chemical reaction not unlike the following:įor the reaction calculate at 298 K from the tabulated standard Gibbs energies of formation.

Chemical reaction thermodynamics calculator