erm dude it really depends on your build, muscle mass, muscle density,
but
you should aim to be tired after about 15 reps, and you should be completely fatigued after about 4 sets of 15 reps, but thats only if your after power/stregth if your after size, increase reps and sets but decrease the weight slightly
weight lifting burns calories so in theory it helps weight loss, but its primarily used for gaining muscle mass, however its been proven more muscle = higher metabolism, which means more calories burned, and you should aim to work a different section of muscles once per week so my workout is
monday
Core- chest, back and shoulders
tuesday
rest day
wednesday
arms lower and upper
thursday
rest day
friday
legs
saturday and sunday
reserved for work and sports
plus a bit of cardio say 30mins running a day wouldnt go a miss