Given the table of pKa values, at a pH of 3.5, which substance(s) exist predominantly in the non-protonated form?

Acid pKa
HNO3 -1.3
HSCN 4.0
HCN 9.4
HOCI 7.4

You have 1 strong acid (HNO3) and three weak ones. The HNO3 ionizes completely, i.e., as H^+ and NO3^- with no HNO3 molecule left behind. All of the others will have at least some of the unionized acid left behind. So.......