Dear kaler ,
In class XI , there is a repetetion of the basics in the first 3 chapters and then some detailed concepts are also introduced.
However it would be very good if you have your basics right for IIT-JEE, if your basics aren't that strong , build on them in class XI by doing the starting chapters thorougly, or class XI will be a lot of stress for you to study chemistry , from class X's 5 chemistry chapters , there is a sudden change to 16 chemistry chapters alone in class XI .
anyway , it is a challenge to face.
BEST OF LUCK