At 60°C, dinitrogen tetroxide is fifty percent dissociated. Calculate the standard free energy change at this temperature and at one atmosphere.

At 60°C, dinitrogen tetroxide is fifty percent dissociated. Calculate

1.	At 60°C, dinitrogen tetroxide is fifty percent dissociated. Calculate the standard free energy change at this temperature and at one atmosphere.
Answer» Solution :`N_(2) O_(4(g)) hArr 2NO_(2(g))` If `N_(2) O_(4)` is 50% dissociated, the mole FRACTION of both the substances is given by `X_(N_(2) O_(4))= (1-0.5)/( 1+0.5) , ""X_("NO"_(2) ) = (2 xx 0.5)/( 1+ 0.5)` `P_(N_(2) O_(4) ) = (0.5)/( 1.5 ) xx 1"atm"` `P_(NO_2) = (1)/( 1.5) xx 1"atm"` The equilibrium CONSTANT `K_(p)` is given by: `K_(P) = ((P_(NO_2))^(2) )/(P_(N_(2) O_(4) )) = (1.5)/( (1.5)^(2) xx (0.5) ) = 1.33 "atm"` Since, `Delta_(r) G^( Theta )= - "RT In" K_(p)` `Delta_(r) G^( Theta ) = (-8.314 "JK"^(-1) "mol"^(-1) ) xx (333 K) (2.303) xx (0.1239)` `= -763.8 "kJ mol"^(-1)`