Hi there,

Below I have enlisted several chapters important for Chemistry  in JEE, check this out:

• Atomic structure
• Gaseous and liquid state
• Electrochemistry
• Chemical kinetics
• Nuclear and surface Chemistry
• Chemical bonding
• D block elements
• Co ordination compound
• Alkyl  halides
• Aromatic compounds
• Thermodynamics
• P block Elements
• General organic chemistry
• Isomerism
• Aldehydes and ketone
• Carboxylic acids and it's derivatives

Check this link for more detailed information: https://engineering.careers360.com/articles/most-important-chapters-of-jee-main

Hope this answer will help you.

Thank you and very good luck:)