According to my experience in Class 11, Ionic Equilibrium, a part of Physical Chemistry is one of the most dreaded and tough subjects.

Besides Ionic, Electrochemistry and Thermodynamics are also considered tough.

On the contrary, Organic Chemistry which is one of the most tough topics of Class 12, is comparatively easy in Class 11 and deals with basic topics like IUPAC, Hydrocarbons and Reaction Mechanism. However General Organic Chemistry, Aromatics and Reaction Mechanism are considered tough and extremely critical to understanding of higher and tougher topics in Class 12.

Hope that Helps.