If you are preparing for JEE 2021 make sure you go through topics from the NCERT before focussing in other entrance exams books. Some of the most important topics where one can find majority of questions are(trend):-

1) Structure of atoms,Mole concept

2) Thermodynamics and Equilibrium(stay focused on NCERT)

3) States of Matter(gas eqns and numericals)

4) S block elements and hydrogen(from NCERT only), learn various trends of elements and some important reactions they from. Exceptions are to studied thoroughly

5) Organic chemistry(except those Determinatio methods like dumas,kjeldahls)

6) p block elements is to be studied thoroughly.

7) In chemical bonding do learn the tables of Various bonding types and ways they can be bonded, VSEPR theory is very important. Expect 1-2 questions.

You can expect around 13-14 questions can be asked from class XI part of the syllabus.

If you study these topics nicely and from NCERT to be specific you can score well in Chemistry.

good luck