If there is nothing on the card put it into your 311 and tell it to format it.
That just cleans it up.

If it fits in that little micro slot it should work.
I have never seen a card that size, I have a couple of the larger 8 GB cards that the Acer 320 uses, and a couple of the tiny cards that go into cellphones.

I also have both a Acer c720 and a Acer Chromebook 311.