Question

the correct formula for nitrous acid is *
a. hno₃(aq)
b. hno₂(aq)
c. nh₃(aq)
d. hno₂(g)

if the classical name of an acidic substance has the ending \...ic acid\, then the formula for the \per....ic acid\ of the same family is obtained by
removing two oxygen atoms
removing all of the oxygen atoms
adding one oxygen atom
subtracting one oxygen atom

Explanation:

First Question (Formula of Nitrous Acid)

• Nitrous acid has the formula $\ce{HNO_2}$. The suffix “-ous” in the acid name (nitrous) corresponds to the lower oxidation state of nitrogen here, and the acid is aqueous (so (aq)). Option a is nitric acid ($\ce{HNO_3}$), c is ammonia, and d has the wrong state (gas instead of aqueous acid).

Second Question (Per...ic Acid Formula Derivation)

In the nomenclature of oxyacids, the “per...ic acid” form has one more oxygen atom than the “...ic acid” form. For example, chloric acid is $\ce{HClO_3}$, perchloric acid is $\ce{HClO_4}$ (one extra O). Removing O would relate to “...ous” or “hypo...ous” forms, not “per...ic”.

Answer:

b. $\ce{HNO_2(aq)}$