Hello,

You haven't mention chemistry for which standard or regarding any entrance exam, in case you're asking this question for JEE MAIN, consider visiting the following link to know important topics, books and more details such like this-

https://engineering.careers360.com/articles/jee-main-important-topics-books

Hey there

If you are preparing for competitive exams then let me tell you that chemistry is the most scoring subject and thus you should prepare it thoroughly. But I'll say the most important part is organic chemistry which will need practice also. For inorganic and physical just read NCERT completely. Almost every chapter is important in chemistry if you want good marks. But since organic is logical so I'll suggest you atleast complete organic thoroughly.

Good luck