In reaction, [math]N_2 O_4\to {2NO_2}_{(g)}[/math], what will be the value of [math]K_C[/math] at 35° C if [math]N_2 O_4[/math] is dissociated to the extent of 20% under a pressure of 1 atmosphere? Which is regarded as a more difficult A level in the UK, Further Maths or Chemistry?