Error in the motivation letter I sent my application to the University of Zurich for my masters studies. However, I just realized that I made a really big mistake in the motivation letter. In the first line of the letter I wrote something like, "With this letter, I would like to express my interest in studying Masters of Science in Physics at the University of Geneva starting from fall 2017."
Does this hampers the chance of getting an admission?
There is nothing you can do about this any more, so it's not worth your brain and emotional power to worry about. Spare your brain for things you can affect.

That said, having seen such mistakes many times in applications, they do seem to suggest a lack of attention to detail. I wouldn't say that we've ever rejected an application because of a mistake of this sort, but they do get noted if they fit into a bigger picture in the application. If you are convinced that your application is otherwise good, then you will not likely have to fear any detrimental effect.

(I'm going to add that everyone who sits on selection committees knows that applicants apply to many different universities. While these sort of mistakes should not happen, we understand that they do and why.)