Question

15 of 20
multiple choice
finish quiz
polyatomic ions
name\tformula
nitrite\tno₂⁻
nitrate\tno₃⁻
sulfite\tso₃²⁻
sulfate\tso₄²⁻
phosphate\tpo₄³⁻
which three examples are correctly matched to the rules they follow?
rules for naming acids:
rule 1: for any acid containing an anion, start with the prefix hydro, then add the first syllable of the anion name and change the suffix to ic.
rule 2: for any acid containing a polyatomic ion ending in ate, change the ending to ic.
rule 3: for any acid containing a polyatomic ion with one less oxygen than the polyatomic ions ending in ate, change the suffix to ous.
zoom
a h₂so₃, sulfurous acid
rule 3
b h₃po₄, phosphoric acid
rule 3
c hno₃, nitric acid
rule 2
d hf, hydrofluoric acid
rule 1
e hcl, hydrochloric acid
rule 2

Explanation:

Step1: Analyze Option A

$H_2SO_3$ has sulfite ion, Rule 3 applies.

Step2: Analyze Option B

$H_3PO_4$ has phosphate ion, Rule 2 applies.

Step3: Analyze Option C

$HNO_3$ has nitrate ion, Rule 2 applies.

Answer:

A. $H_2SO_3$, sulfurous acid (Rule 3)
B. $H_3PO_4$, phosphoric acid (Rule 2)
C. $HNO_3$, nitric acid (Rule 2)
D. $HF$, hydrofluoric acid (Rule 1)
E. $HCl$, hydrochloric acid (Rule 1)

Let's check each option:

• Option A: Sulfate is $SO_4^{2 - }$ and sulfite is $SO_3^{2 - }$. $H_2SO_3$ contains sulfite which has one - less oxygen than sulfate. According to Rule 3, for an acid containing a polyatomic ion with one - less oxygen than the polyatomic ion ending in 'ate', we change the suffix to 'ous'. So $H_2SO_3$ is sulfurous acid, and this option is correct.
• Option B: Phosphate is $PO_4^{3 - }$. According to Rule 2, for an acid containing a polyatomic ion ending in 'ate', we change the ending to 'ic'. So $H_3PO_4$ is phosphoric acid. This option is correct.
• Option C: Nitrate is $NO_3^{-}$. According to Rule 2, for an acid containing a polyatomic ion ending in 'ate', we change the ending to 'ic'. So $HNO_3$ is nitric acid. This option is correct.
• Option D: $HF$ contains the fluoride anion ($F^{-}$). According to Rule 1, for an acid containing an anion, we start with the prefix 'hydro -', then add the first syllable of the anion name and change the suffix to 'ic'. So $HF$ is hydrofluoric acid. This option is correct.
• Option E: $HCl$ contains the chloride anion ($Cl^{-}$). According to Rule 1, for an acid containing an anion, we start with the prefix 'hydro -', then add the first syllable of the anion name and change the suffix to 'ic'. So $HCl$ is hydrochloric acid, not following Rule 2. This option is incorrect.

So the correct options are A, B, C, D. But since we need to choose three, we can choose A, B, C as they are clear - cut examples of the rules.