With a 12th cutoff score of 170 and belonging to the BC (Backward Classes) category, you might be able to secure a government seat in Tamil Nadu for B.Sc. Nursing in round 1, but it's not guaranteed. The availability of seats and the overall cutoff scores for BC category students will determine your chances.

Here's a more detailed breakdown:

NEET Scores:

While your 12th cutoff is relevant, B.Sc. Nursing admission is typically based on NEET (National Eligibility cum Entrance Test) scores.

BC Category:

The BC category in Tamil Nadu has a reservation quota, which can improve your chances of getting a seat.

College-Specific Cutoffs:

Cutoffs for B.Sc. Nursing vary from college to college.

Round 1:

Round 1 admissions are usually the most competitive, so securing a seat might depend on the overall performance of other BC candidates.

Factors Affecting Cutoffs:

Several factors, including the number of students applying, the difficulty level of the NEET exam, and the availability of seats, influence cutoffs.

Checking Cutoffs:

You should consult the previous year's cutoffs for the government medical colleges in Tamil Nadu to get an idea of the minimum scores required for admission.

In conclusion, while a 12th cutoff of 170 and being from the BC category are positive factors, the final outcome of round 1 admission will depend on your NEET score, the overall competition, and the specific college cutoff for B.Sc. Nursing.