Question

At `60^(@)C`dinitrogen tetroxide is fifty percent dissociated. Calculate the standard free energy change a this tempeature and one atmosphere.

Answer 1

`{:(,N_(2)O_(4)(g),hArr,2NO_(2)(g)),("Initial amount",1"mole",,0),("At eqm.",1-0.5=0.5 "mol",,0.5 xx 2 =1 "mol Total"= 1.5 "mol" ):}`
`p_(N_(2)O_(4))= (0.5)/(1.5) xx1atm=(1)/(2) atm,p _(NO_(2))= (1)/(1.5) xx1 atm (2)/(3) atm`
`K_(p)= (p_(NO_(2)))/( p_(N_(2)O_(4)))= ((2//3)^(2))/((1//3))= 1.33atm`
`Delta_(r)G^(@) = - 2.303 RT log K_(p) = - 2.303 ( 8.314JK^(-1) mol^(-1)) ( 333K) log 1.33 = -790 J mol^(-1)`