Why don t you need to identify the gases in Dalton s Law of Partial Pressures?

Because Dalton's law basically deals with ideal gases, and all ideal gases are essentially the same. They follow the assumptions of the kinetic molecular theory:

1. Gas molecules are in constant random motion and their speeds are determined by the absolute temperature.

2. Gases are essentially points with no volume.

3. Gases do not attract or repel each other.

4. All collisions are completely elastic.