Are these correct? If not, why? What do they mean?
1. What kind of pants are these?
2. What kind of pants is these?
Pants (or trousers to us BrE speakers) are slightly odd in that they are considered plural. I am wearing a pair of trousers. They are black and do not have any pockets.

I don't know why...two legs? But then jumpers (sweaters) have two arms and are not talked about in the plural.

So anyway, 1 is correct.
I have been searching for an explanation (the things we do!) The only one I can come up with is that perhaps originally 'pants' comprised 2 separate legs which were tied around the waist. I believe this is the case for the first women's undergarments.
Students: We have free audio pronunciation exercises.
What about this:

1. What pair of pants is this?
2. What pair of pants are these? (Incorrect?)
 abbie1948's reply was promoted to an answer.
Students: Are you brave enough to let our tutors analyse your pronunciation?