How much weight per arm should i lift (what weight is normal) in order to train my chest, biceps, and similar muscles. i am sport active and in shape.

Work up to it: Different trainers will tell you different things. Here's what's i've been told most often and have found helpful. Start off with a weight that is comfortable for you. Try to do three sets of ten reps three times a week. Increase the weight whenever you are able. Especially at your age, you will notice that your strength increases rapidly.

Start with a weight: You can easily and safely lift and perform that lift at least 10 times (repetitions) and then repeat at least 1 time again (a set). That would mean lifting the same weight 20 times (2 sets of 10 reps each). For larger muscles, do heavier weights fewer reps (generally) and for more strength, do slightly less weight, but more reps (15-20 per set) and 3 or more sets.