Jonas is chosen to be the new Receiver of Memory at the very end of chapter 8. The reader learns about his emotional state at the end of that chapter and throughout chapter 9.
After Jonas's job is announced to the community, everybody begins chanting his name. Jonas feels honored and proud at this moment. . . and terrified all at the same time. He knows it's an honor and a big responsibility.
His heart swelled with gratitude and pride. But at the same time he was filled with fear. He did not know what his selection meant. He did not know what he was to become. Or what would become of him.
Then chapter 9 begins, and Jonas's feelings begin to change to dread and loneliness.
Now, for the first time in his twelve years of life, Jonas felt separate, different. He remembered what the Chief Elder had said: that his training would be alone and apart.
The full impact of what he has been assigned hits, and Jonas is scared. The Receiver of Memory is not a common assignment. To make matters worse, the previous Receiver flunked out and was never heard from again. In fact, her name is forbidden to be spoken. That's a big deal in Jonas's community. To make matters worse, his parents refuse to talk about what happened to the previous Receiver.
But his parents looked blank. "We don't know," his father said uncomfortably. "We never saw her again."
As Jonas reads through his training instructions, he learns that he is not allowed to discuss any of his training with other people. That compounds his feelings of solitude. By the end of chapter 9, it is clear that Jonas is not glad to be the new Receiver of Memory.