Hi kashish,

I think you are asking about board exams of class 12th.

Otherwise if you are asking for any entrance exam then I would suggest you to study all the chapters as nobody knows what will came in the examination. So better prepare all chapters for better understanding.

See, all the chapters are important and the ones who have mentioned are of class 11th and class 12th. So equilibrium,  thermodynamics are one  of the important chapters that will help you in getting good marks as major portion comes from this .

Solve a good number of questions of these chapters and then go fir the examination.

See, selected chapters will not help you to score good marks so you should prepare the whole course.

Hope you understand.

Thank you and very good luck:))