sir in class 12th result i have decleared pass due to 6 subjects but chemistry becomes my additional subject so i am eligible for ssc chsl / cgl.
for ssc cgl basic requirement is one need to be completed his/her graduation. For ssc chsl basic requirement is one need to be completed his / her 12th. In your case you already got pass certificate of 12th, so yes you are eligible for ssc chsl exam. Also you can add chemistry as an additional qualification or as an addition certification.
hope this is helpful to clear your dilemma.