Question

Which is an incorrect formula for a compound containing phosphorus.

1- P4O10 2- H2PO4 3- KPF6 4- Na2HPO3 5- Ca2P

A) 3 B) 3 & 4 C) 1 & 5 D) 2 & 5 E) 1 F) 4 G) 3 & 5

Answer 1

I think #5 is incorrect but not sure what else.

Answer 2

I almost didn't figure out how you numbered/lettered. You mixed them up from question to answer and the 1- and 2- and 3- I thought were subscripts.
Ca2P should be Ca3P
H2PO3 should be (H2PO3)^-