Recipe says to bake chicken at 250 degrees for 5 hrs. how long does it need to be baked at 350 degrees?

Yes, you can.

In fact, one of the biggest, ever so often repeated mantras here is:

Don't determine doneness with a watch, use a thermometer!

Measure at the thickest part of the thigh, not touching the bone. If you have reached at least 165°F or 75°C, your chicken is done.

Of course, the hotter your oven, the crispier the skin will be and the higher the risk of burning some parts, so check your chicken periodically and tent with aluminum foil if necessary. That said, 350°F / 175°C is a perfectly reasonable temperature to roast a chicken.

I won't and can't give you a time to bake the chicken, partly because I don't know how large your bird is and what temperature it was at the start, because I don't know how reliable your oven thermostat is and above all: because only a thermometer can guarantee that the meat reached a safe temperature.

You certainly can cook the chicken at 350 but you will not get the same result. 250 for five hours will get an extremely tender, falling off the bones result as it allows time for the muscle fibers to completely relax and soften. 350 for an hour to two hours will just be an ordinary cooked chicken.

Hmm, never heard of cooking chicken at 250 degrees. When cooking a whole chicken at 350, you just time it a half hour per pound; so,say a 3 pound bird would take an hour and a half. If the chicken is stuffed, make sure to add at least 15-20 minutes to the cooking time... and check doneness with a thermometer for safety!!

I once wanted to thaw a frozen chicken. I usually turn the oven on and when it reaches 250 degrees turn it off and put whatever you want to thaw. Come back an hour or two later and it will be perfectly thawed. However, I threw the chicken in, forgot to turn off the heat went out for the day and completely forgot about it. I came home to the best roast chicken I've had to this day. The legs were hanging relaxed from the body the skin was crisp and perfect and it wasn't even seasoned. Tonight I'm going to cook at 250 because it's too hot to cook during the day for 2 hrs at 350.