What are the main changes between pmpok 4 th edition and pmpok 5th edition ? In which chapters ?

The biggest change in the5th Edition is a new knowledge area called Stakeholder Management. In the4th Edition there were processes such as indentify stakeholders and manage stakeholder expectations, however there was no knowledge area for stakeholder management. 

There are also various changes to the Planning process groups like the Plan Scope, Schedule, and Cost management processes. These were part of the Scope, Time and Cost Management knowledge areas.

There are other numerous changes within the processes and some new concepts were added. 

The most major change is addition of a new knowledge area in PMBOK5th edition by the name of stakeholders management. Which was earlier covered under communication management.

Due to the new adition the total number of process now are47 processes further some changes into planning, scope, schedule management have also taken place but they are somehow related with addition of the stakeholder knowledge area.

Hence to summarize as per PMBOK5th edition. Total knowledge areas are now -10 with47 processes.