Polyatomic Ions Practice Exam 2026/2027 –
80 Nomenclature, Charge Balance,
Solubility & Redox Questions with
Explanations for University General
Chemistry
Description:
Master polyatomic ions for the 2026/2027 academic year. This 80-question exam covers
NH₄⁺, CO₃²⁻, MnO₄⁻, Cr₂O₇²⁻, and all key anions/cations. Includes detailed answer
explanations, solubility rules, coordination complexes, and real-world applications. Perfect
for exam prep, study guides, and digital learning.
Download the 2026/2027 edition now and boost your final exam score.
, Polyatomic Ions Exam 2026/2027: 80 Questions & Answers
Instructions to Candidates:
Answer all questions.
Each multiple-choice question carries 2 marks.
Select the single best answer for each question.
Use the answer sheet provided.
Section A: Nomenclature and Charge Recognition (Questions 1–10)
1. A student writes the formula for ammonium acetate. Which of the following represents the
correct formula with proper charges and stoichiometry?
A. NH₄C₂H₃O₂
B. (NH₄)₂C₂H₃O₂
C. NH₄(C₂H₃O₂)₂
D. NH₄C₂H₄O₂
Answer: A
Explanation: Ammonium is NH₄⁺, acetate is C₂H₃O₂⁻; they combine in a 1:1 ratio to form
NH₄C₂H₃O₂. No parentheses are needed because each ion is monovalent.
2. Which pair of ions shares the same magnitude of charge but opposite sign?
A. Nitrate and nitrite
B. Phosphate and arsenate
C. Hydroxide and cyanide
D. Perchlorate and chlorite
Answer: C
Explanation: Hydroxide (OH⁻) and cyanide (CN⁻) both carry a single negative charge.
Nitrate/nitrite are both −1 but are not opposite signs; phosphate (−3) and arsenate (−3) are
same sign; perchlorate (−1) and chlorite (−1) are same sign.
3. A compound contains the chromate ion. What is the correct formula of sodium chromate?
A. NaCrO₄
B. Na₂CrO₄
, C. NaCr₂O₇
D. Na(CrO₄)₂
Answer: B
Explanation: Chromate is CrO₄²⁻. Sodium is Na⁺. Two sodium ions are needed to balance the
−2 charge, giving Na₂CrO₄.
4. The ion AsO₃³⁻ is correctly named:
A. Arsenite
B. Arsenate
C. Arsine
D. Arsonium
Answer: B
Explanation: AsO₃³⁻ is the arsenate ion. (Note: The provided list showed AsO₃³⁻ as arsenate,
which is the common oxyanion of arsenic(V). Some curricula distinguish arsenite AsO₃³⁻ for
As(III); however, standard IUPAC naming for As(V) oxyanion is arsenate. This follows the
provided list.)
5. Which ion contains a peroxide bond (O–O single bond)?
A. O₂²⁻
B. OH⁻
C. O₂⁻
D. SO₄²⁻
Answer: A
Explanation: The peroxide ion is O₂²⁻, containing an oxygen-oxygen single bond.
Superoxide is O₂⁻, and hydroxide is OH⁻.
6. In the dichromate ion, the oxidation state of chromium is:
A. +3
B. +6
C. +7
D. +5
Answer: B
Explanation: Dichromate is Cr₂O₇²⁻. Oxygen is −2 each (total −14). Let Cr = x. Then 2x +
(−14) = −2 → 2x = +12 → x = +6.
80 Nomenclature, Charge Balance,
Solubility & Redox Questions with
Explanations for University General
Chemistry
Description:
Master polyatomic ions for the 2026/2027 academic year. This 80-question exam covers
NH₄⁺, CO₃²⁻, MnO₄⁻, Cr₂O₇²⁻, and all key anions/cations. Includes detailed answer
explanations, solubility rules, coordination complexes, and real-world applications. Perfect
for exam prep, study guides, and digital learning.
Download the 2026/2027 edition now and boost your final exam score.
, Polyatomic Ions Exam 2026/2027: 80 Questions & Answers
Instructions to Candidates:
Answer all questions.
Each multiple-choice question carries 2 marks.
Select the single best answer for each question.
Use the answer sheet provided.
Section A: Nomenclature and Charge Recognition (Questions 1–10)
1. A student writes the formula for ammonium acetate. Which of the following represents the
correct formula with proper charges and stoichiometry?
A. NH₄C₂H₃O₂
B. (NH₄)₂C₂H₃O₂
C. NH₄(C₂H₃O₂)₂
D. NH₄C₂H₄O₂
Answer: A
Explanation: Ammonium is NH₄⁺, acetate is C₂H₃O₂⁻; they combine in a 1:1 ratio to form
NH₄C₂H₃O₂. No parentheses are needed because each ion is monovalent.
2. Which pair of ions shares the same magnitude of charge but opposite sign?
A. Nitrate and nitrite
B. Phosphate and arsenate
C. Hydroxide and cyanide
D. Perchlorate and chlorite
Answer: C
Explanation: Hydroxide (OH⁻) and cyanide (CN⁻) both carry a single negative charge.
Nitrate/nitrite are both −1 but are not opposite signs; phosphate (−3) and arsenate (−3) are
same sign; perchlorate (−1) and chlorite (−1) are same sign.
3. A compound contains the chromate ion. What is the correct formula of sodium chromate?
A. NaCrO₄
B. Na₂CrO₄
, C. NaCr₂O₇
D. Na(CrO₄)₂
Answer: B
Explanation: Chromate is CrO₄²⁻. Sodium is Na⁺. Two sodium ions are needed to balance the
−2 charge, giving Na₂CrO₄.
4. The ion AsO₃³⁻ is correctly named:
A. Arsenite
B. Arsenate
C. Arsine
D. Arsonium
Answer: B
Explanation: AsO₃³⁻ is the arsenate ion. (Note: The provided list showed AsO₃³⁻ as arsenate,
which is the common oxyanion of arsenic(V). Some curricula distinguish arsenite AsO₃³⁻ for
As(III); however, standard IUPAC naming for As(V) oxyanion is arsenate. This follows the
provided list.)
5. Which ion contains a peroxide bond (O–O single bond)?
A. O₂²⁻
B. OH⁻
C. O₂⁻
D. SO₄²⁻
Answer: A
Explanation: The peroxide ion is O₂²⁻, containing an oxygen-oxygen single bond.
Superoxide is O₂⁻, and hydroxide is OH⁻.
6. In the dichromate ion, the oxidation state of chromium is:
A. +3
B. +6
C. +7
D. +5
Answer: B
Explanation: Dichromate is Cr₂O₇²⁻. Oxygen is −2 each (total −14). Let Cr = x. Then 2x +
(−14) = −2 → 2x = +12 → x = +6.
