Why is my mom so angry and unhappy every time she comes home?

Every time my mom comes home (whether that be from vacation, work, or just after a lot of errands) she is so angry and starts handing out chores to my brothers and I that she never even told us to do in the first place. Also, she got back from a vacation and before she even talked about her trip she just goes off about what things are not the way she wanted them. She will also ask us of things she has never asked before such as planning an itinerary for our trip when she and my dad are the ones that have done that for every trip I have ever been on in my life. But the ways she says it makes it sound like I'm the one who is wrong for not doing something no one has ever asked me to do.I'm 17 now but she has been doing this for four years now and now that I am graduating high school (with good grades, going to a good college, no problems with the law, pretty much.... I'm a good kid and so are my brothers but she is never happy with us). She is completely blind to the fact that she does this 99% of time she comes back and regardless, she just blames all her problems on my brothers and I. I don't know if this is just how she is as a person or if something else is bothering her but it really annoys me. Anyone else have a similar situation they had to deal with and how did you deal with it? (I've tried just doing all the chores and retarded crap she asks me but she just explodes over the smallest things that my brothers I do wrong. I have also tried asking her about work and seeing if that was related but its not the reason every time)