Answer
(a) hydrofluoric acid
(b) bromic acid
(c) $H_3PO_4$
(d) $HNO_2$
Work Step by Step
(a) For an acid containing hydrogen bonded to a halogen, we take the first part of hydrogen, $hydro-$, combine it with the first part of the name of the halogen with the ending changed to $-ic$, and add the word $acid$ to the end.
For $HF$, we name it hydrofluoric acid.
(b) For acids containing oxoanions, we merely take the name of the oxoanion, change its ending to $-ic$, and adding the word $acid$ to the end.
For $HBrO_3$, we name it bromic acid.
(c) Here, we have another oxoanion bonded to hydrogen. $PO4$ is called phosphate. Hydrogen has an oxidation number of $1+$ here whereas phosphate has an oxidation number of $3-$; therefore, we need three hydrogens for each phosphate. Thus, phosphoric acid has the formula $H_3PO_4$.
(d) Acids having the ending $-ous$ means that the oxoanion has the $-ite$ ending. In this acid, hydrogen is bonded to the nitrite ion ($NO_2^-$). Thus, nitrous acid has the formula $HNO_2$.
