# What is reaction isotherm? Describe briefly.

##### 1 Answer

Jul 17, 2017

The **reaction isotherm** is given by

#DeltabarG_(rxn) = DeltabarG_(rxn)^@ + RT ln ((Pi_(j) a_j^(nu_j))/(Pi_(i) a_i^(nu_i)))# ,where:

#DeltabarG_(rxn)# is the**molar Gibbs' free energy**for the reaction.#DeltabarG_(rxn)^@# is the molar Gibbs' free energy for the reaction at the(*standard pressure*#"1 bar"# ) and at the temperature of the reference reaction.#R# and#T# are known from the ideal gas law;#T# is in#"K"# .- The argument of
#ln# is the general form of the**reaction quotient**,#Q# , which for real gases and solutions, utilizes**activities**#a# for the#i# th reactant and#j# th product.

An example for the activity is#a_i -= f_i/P^@# for gases, where#f# is the fugacity (the real-gas partial pressure). Or, if you know the mol fraction#chi_i# of substance#i# in the solution,#a_i = gamma_i chi_i# , where#gamma_i# is the activity coefficient of substance#i# at that#T# and#P# .

This is generally useful for determining

It's also important that