HNO2 Acid Name
The keyword “hno2 acid name” asks for the correct nomenclature of the oxoacid \( \mathrm{HNO_2} \). Oxoacids are named by identifying the corresponding oxyanion and then applying a consistent suffix change.
Direct name: \( \mathrm{HNO_2} \) is nitrous acid.
The name comes from the nitrite ion \( \mathrm{NO_2^-} \) using the rule “-ite” \(\rightarrow\) “-ous acid.”
Step-by-step naming from the oxyanion
For an oxoacid \( \mathrm{H_{x}AO_{y}} \), remove \( \mathrm{H^+} \) conceptually to find the oxyanion \( \mathrm{A O_y^{\,n-}} \), then translate the anion name into the acid name.
-
Identify the oxyanion. Removing one \( \mathrm{H^+} \) from \( \mathrm{HNO_2} \) gives the conjugate base:
\[ \mathrm{HNO_2 \;\rightleftharpoons\; H^+ + NO_2^-} \]
The anion \( \mathrm{NO_2^-} \) is called nitrite.
-
Apply the oxoacid suffix rule.
- -ite (anion) \(\rightarrow\) -ous acid (acid)
- -ate (anion) \(\rightarrow\) -ic acid (acid)
Since the anion is nitrite, the acid is nitrous acid.
Quick comparison table (avoids the most common mix-up)
| Oxyanion | Oxyanion name | Corresponding acid | Acid name | Suffix pattern |
|---|---|---|---|---|
| \( \mathrm{NO_2^-} \) | nitrite | \( \mathrm{HNO_2} \) | nitrous acid | -ite \(\rightarrow\) -ous |
| \( \mathrm{NO_3^-} \) | nitrate | \( \mathrm{HNO_3} \) | nitric acid | -ate \(\rightarrow\) -ic |
Common error: Calling \( \mathrm{HNO_2} \) “nitric acid.” Nitric acid corresponds to nitrate \( \mathrm{NO_3^-} \), not nitrite \( \mathrm{NO_2^-} \).
Visualization: from anion name to acid name
Final answer
The acid name of \( \mathrm{HNO_2} \) is nitrous acid, because its conjugate base is the nitrite ion \( \mathrm{NO_2^-} \) and nitrite-type oxoacids take the “-ous acid” ending.