The closest category here for a Spring Peeper would be under the "Tree Frog" section, they belong to the Hylidae family and used to even be called Hyla crucifer.

I'm not very familiar with the Mountain Chorus Frog, but they often have a light coloured triangular blotch under their eye that a Peeper lacks, don't always have the characteristic cross on the back like a Peeper, and spend more time away from water. Their call is also quite different. Here's a couple of species accounts that include tadpole descriptions:

Mountain Chorus Frog « PA HERP IDENTIFICATION
Northern Spring Peeper « PA HERP IDENTIFICATION

Here are two more species accounts that include recordings of their calls:

Mountain Chorus Frog
Northern Spring Peeper

Check with your local fish and wildlife department about the legality of collecting tadpoles or wild frogs. Peepers are pretty common in their range so are often ok to collect but local laws may vary. Mountain chorus frogs are described as 'special concern' or 'in decline' in some of the descriptions I was just looking at, so it's also possible they would be protected where you are but Peepers aren't.

It sounds like you are in possession of a frog now? Photographs might help people ID it for you. Include a picture of the side of the face and back if possible.