hi,

see you can take any of the subject as optional paper for jammu and kasmir combined services competitive exam,

1) Agriculture:

2) Animal Husbandry and Veterinary Science:

3) Anthropology:

4) Botany:

5) Chemistry:

6) Civil Engineering:

7) Commerce and Accountancy:

8) Economics:

9) Electrical Engineering:

10) Geography:

11) Geology;

12) History:

13) Law;

14) Management;

15) Mathematics;

16) Mechanical Engineering;

17) Medical science;

18) Philosophy;

19) Physics;

20) Political Science & International Relations;

21) Psychology;

22) Public Administration:

23) Sociology;

24) Statistics;

25) Zoology;

26) Literature of any one of the following languages:

Arabic, Dogri, English, Hindi, Kashmiri, Persian, Punjabi,

Sanskrit and Urdu.

since chemistry is included in the list you can surely take chemistry as optional subject.