Here is an example of them both being used:
Although the baby was able to stand while holding on to something, he was still unable to walk.
I am able to go to the mall this weekend, are you?
Completely devoid of fuel, she collapsed in a shivering heap and was unable to mine any more diamonds.
She was able to transcend her own suffering to help others.
The able sailor rove the line quickly through the block.
It is a generalization to say that tall people can play basketball well when, in fact, you need to be able to play well and if you're tall it is an advantage.
The dictator attempted to suppress any opposition to his rule by silencing dissidents and controlling the media.
I was unable to go to the carnival because I had loads of homework.
It's so frustrating that I can't fix it myself, but I am unable to lift it.
"we were unable to get expiation from the local store"
We were unable to avoid drifting into the shoal.
I am unable to describe the cumulonimbus clouds effectively.
The Zenger Trial in 1735 set a precedent for freedom of the press in colonial America when John Peter Zenger, a printer, was acquitted of seditious libel charges after publishing critical articles about the colonial governor of New York.
It is not acceptable to be unable to use acceptable in a sentence.
I was unable to use the computer for a while, as it was busy updating the system.
He was injured and therefore unable to play in the final round.
The cart was unable to bear the heavy load.
No, the correct sentence should be: "The beneficiary is unable to speak due to her disabilities." "Due to" is the correct phrase to use in this context.