Can someone tell me if this sentence is an appositive phrase:
The blacks, were the lowest ranking class in society.
No, it isn't. An appositive must rename the noun it is referring to.
No, the sentence you provided does not contain an appositive phrase.
An appositive phrase is a noun or noun phrase that renames or identifies another noun or pronoun in a sentence. It provides additional information about the noun or pronoun it is referring to.
To determine if a sentence includes an appositive phrase, you need to look for a noun or noun phrase that is directly next to another noun or pronoun, and adds extra information about it.
In the sentence you provided, there is no noun or noun phrase directly next to "blacks" that renames or identifies it. Therefore, it does not meet the criteria for an appositive phrase.