Is this Queen trapped?

I was solving a puzzle and pushed a4-a5, then computer Qxb5. 

I didn't think so, either.

a4-a5 looks correct and Qxb5 also looks correct.

Black gets two pieces for the Q and is losing. The alternative is Qc6 and Nxe5 and black still has to take the N with the Q. Otherwise, black loses a N and a R and is losing.

The queen is not trapped, but it cannot keep safe and defende the knight on c7 at the same time. If the queen moves to saftey, wihte has Kxc7, forking the King and Rook, therefore not only winning a rook, but also destorying blacks defenses. That's why the computer thinks giving up the queen for the knight is the best option.

After a5 you will gain some material for sure. Apart for the queen the threat is Nxc7+, so queen has to keep being taken and it needs to disallow Nxc7+. So the only move to do both is Qc6. But white plays Nxe5 attacking the queen again and now Nxc7+ is unstoppable unless you give up the queen.

Thanks everyone.  My next step is to understand just what kind of pressure the move puts on white.  iow, if I do this............  I'm only at if I do this.. 

Well, black ends up with a bishop on b5 but no other pieces capable of combining in some kind of tactical counter-attack, so it's a win for white.

Black could retreat their queen, but at the cost of their knight, their rook, and their castling rights. You could sac the queen for a knight and a bishop which is a lot better, but you at least have the choice not to if you want to keep the queen no matter what.

I don't know... If I was White in this game, I moved a-pawn... onto a5.

Is that correct?

Really ?

It's strange. Very stupid computer.

The old model... maybe. )

Don't you think that Queen g6 for Black would be better?