@Brian sorry for the unclear formatting but what i wanted to say is,if initially a moles of gas were there and in equilbrium say x have reacted,then 2x(in this case) moles of product would have been formed,since 1 mole of reactant gives 2 moles of products.

@Brian can we do the same thing to pressure as well?i.e. if initially total pressure(i.e. pressure of reactant) is p, and in equilbrium partial pressure of reactant has decreased by y,then can we say partial pressure of product is 2y,since 1 mole of reactant will give 2 moles of product.and is x=y?i.e. is decrease in pressure of reactant equal to decrease number of moles of reactant(or number of moles reacted)?

@Ajay As long as the ideal gas approximation holds: Yes.

(It should hold with NO2 & N2O4.)

thank you very much sir,i have my exams in a few weeks and this is really helpful