Can someone tell me if this is an appositive phrase:

The last class, blacks, were the lowest in society.

Yes, that's an appositive between the two commas.

Thanks for your help

You're very welcome.

Yes, "blacks" in the sentence is an appositive phrase.

An appositive phrase is a noun phrase that renames or provides additional information about a noun or pronoun in a sentence. In this case, "blacks" is providing additional information about "the last class."

To identify an appositive phrase, you can look for a noun or pronoun placed next to another noun or pronoun and separated by commas. In the given sentence, "blacks" follows the comma and describes "the last class," qualifying it as an appositive phrase.