- α )+ ( 2 α ) ▁which ▁is ▁equivalent ▁to ▁ 1 + α . ▁Thus , ▁subst itut ing ▁the ▁mole ▁fra ctions ▁with ▁actual ▁values ▁in ▁term ▁of ▁alpha ▁and ▁simpl ifying ; ▁ ▁This ▁equation ▁is ▁in ▁accord ance ▁with ▁Le ▁Ch atel ier ' s ▁Princi ple . ▁K p ▁will ▁remain ▁constant ▁with ▁temperature . ▁The ▁addition ▁of ▁pressure ▁to ▁the ▁system ▁will ▁increase ▁the ▁value ▁of ▁p T ▁so ▁α ▁must ▁decrease ▁to ▁keep ▁K p ▁constant . ▁In ▁fact , ▁increasing ▁the ▁pressure ▁of ▁the ▁equilibrium ▁fav ours ▁a ▁shift ▁to ▁the ▁left ▁favour ing ▁the ▁formation ▁of ▁d init ro gen ▁t etro x ide ▁( as ▁on ▁this ▁side ▁of ▁the ▁equilibrium ▁there ▁is ▁less ▁pressure ▁since ▁pressure ▁is ▁proportional ▁to ▁number ▁of ▁mol es ) ▁hence ▁decre asing ▁the ▁extent ▁of ▁dis soci ation ▁α . ▁ ▁Ac ids ▁in ▁a que ous ▁solution ▁ ▁The ▁reaction ▁of ▁an ▁acid ▁in ▁water ▁sol vent ▁is ▁often ▁described ▁as ▁a ▁dis soci ation ▁H A ▁< => ▁{ H + } ▁+ ▁{ A ^- } ▁where ▁H A ▁is ▁a ▁pro ton ▁acid ▁such ▁as ▁ac etic ▁acid , ▁CH 3 CO OH . ▁The ▁double ▁arrow ▁means ▁that ▁this ▁is ▁an ▁equilibrium ▁process , ▁with ▁dis soci ation ▁and ▁recom bin ation ▁occurr ing ▁at ▁the ▁same ▁time . ▁This ▁implies ▁that ▁the ▁acid ▁dis soci ation ▁constant ▁ ▁However ▁a ▁more ▁accurate ▁description ▁is ▁provided ▁by ▁the ▁Br ø n