Is process address space part of Process Control Block(PCB)?
Let me start off like this.

The process state includes all the registers that the process may be using, especially the Program counter, plus any other operating system-specific data that may be necessary. This is usually stored in a data structure called a process control block (PCB) or switch frame.
This is what happens in context switching.
The PCB is stored on a per-process stack in kernel memory (as opposed to the user-mode call stack), or there may be some specific operating system-defined data structure for this information.
When a process is ready to run again, its PCB is restored. The program counter from the PCB is loaded, and thus execution can continue in the chosen process.
So, the process's address space is not a part of the PCB data structure.