... reactant, the double-headed arrow (↔) meansthat both the forward and reverse reactions occur (typically at different rates),k is an index from 1 to n products, pk is the number of moles of ... 617Appendix HEquilibrium PrimerConsider a general reaction:or equivalently(H.1)Here, j is an index from 1 to m reactants, rj refers to the number of moles of the jth reactant, Rj ... enclosed species. Ifwe wish to express Keq in terms of mole fraction rather than concentrationfor gases, then, using the ideal gas law, we obtain(H.3)rr pp11 22 11 22RR PP++↔++$$rpjjjmkkknR==∑∑↔11PKpprrk=⎡⎣⎤⎦⎡⎣⎤⎦⎡⎣⎤⎦⎡⎣⎤⎦=⎡⎣⎤⎦PPRRP12121212$$ppknjrjmkj==∏∏⎡⎣⎤⎦11RKPRTyyyyss...