Rucete ✏ AP Chemistry In a Nutshell
3. Ionic Compounds, Formulas, and Reactions — Practice Questions 2
This chapter introduces naming ionic compounds, predicting charges, identifying reaction types, and writing ionic and net ionic equations.
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(Multiple Choice — Click to Reveal Answer)
1. Which of the following correctly predicts the charge on a nitrogen ion?
(A) +3
(B) –2
(C) –3
(D) +5
Answer
(C) — Nitrogen gains three electrons to complete its octet, forming N³⁻.
2. Which pair of elements will most likely form an ionic compound?
(A) C and H
(B) N and O
(C) Na and F
(D) Cl and Br
Answer
(C) — Na (metal) and F (nonmetal) form a typical ionic compound.
3. Which of the following best explains why ionic compounds have high melting points?
(A) They contain metallic bonds.
(B) They consist of strong electrostatic attractions.
(C) They are composed of molecules.
(D) They contain weak intermolecular forces.
Answer
(B) — Ionic compounds have strong Coulombic forces between ions.
4. What type of compound is Ca(NO₃)₂?
(A) Covalent compound
(B) Binary compound
(C) Ionic compound with polyatomic ions
(D) Organic compound
Answer
(C) — Calcium nitrate contains a metal and a polyatomic ion.
5. The correct name for Na₂O is:
(A) Sodium oxide
(B) Disodium monoxide
(C) Sodium(I) oxide
(D) Sodium dioxide
Answer
(A) — Na⁺ and O²⁻ combine to form sodium oxide.
6. What is the balanced formula for aluminum oxide?
(A) Al₂O₃
(B) AlO
(C) Al₃O₂
(D) AlO₂
Answer
(A) — Al³⁺ and O²⁻ combine in a 2:3 ratio to balance charges.
7. Which of the following correctly describes a double replacement reaction?
(A) A + B → AB
(B) AB → A + B
(C) AB + CD → AD + CB
(D) A + BC → AC + B
Answer
(C) — Double replacement reactions involve exchange of ions.
8. What is the correct name for FeCl₃?
(A) Iron chloride
(B) Iron(II) chloride
(C) Iron(III) chloride
(D) Ferric trichloride
Answer
(C) — Fe³⁺ is iron(III), so the name is iron(III) chloride.
9. Which of the following statements is false regarding ionic compounds?
(A) They are generally soluble in water.
(B) They conduct electricity in molten or aqueous states.
(C) They are made of discrete molecules.
(D) They have high melting points.
Answer
(C) — Ionic compounds form lattices, not molecules.
10. Which of the following is a correct net ionic equation?
(A) Na⁺ + Cl⁻ → NaCl
(B) Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
(C) K⁺(aq) + NO₃⁻(aq) → KNO₃(aq)
(D) Pb(NO₃)₂(aq) + 2KI(aq) → PbI₂(s) + 2KNO₃(aq)
Answer
(B) — This shows only the ions that form a precipitate.
11. Which formula is incorrect for the given name?
(A) Calcium bromide — CaBr₂
(B) Iron(II) nitrate — Fe(NO₃)₂
(C) Copper(I) sulfate — CuSO₄
(D) Ammonium carbonate — (NH₄)₂CO₃
Answer
(C) — CuSO₄ contains Cu²⁺, so it's copper(II) sulfate, not copper(I).
12. What happens to the solubility of most ionic compounds with increasing temperature?
(A) Decreases
(B) Increases
(C) Remains unchanged
(D) Becomes zero
Answer
(B) — Most ionic solids dissolve better at higher temperatures.
13. What is the formula for a compound formed between Al³⁺ and S²⁻?
(A) Al₂S
(B) AlS₂
(C) Al₂S₃
(D) Al₃S₂
Answer
(C) — Charges balance in a 2:3 ratio to form Al₂S₃.
14. Which is an example of a covalent compound?
(A) NaCl
(B) NH₃
(C) MgO
(D) CaBr₂
Answer
(B) — NH₃ contains only nonmetals and forms covalent bonds.
15. What is the charge on phosphorus in the phosphate ion (PO₄³⁻)?
(A) –3
(B) +3
(C) +5
(D) –5
Answer
(C) — The overall ion is –3 and oxygen contributes –8; phosphorus must be +5.
16. Which of the following salts will form a neutral solution in water?
(A) NH₄Cl
(B) NaCH₃COO
(C) NaCl
(D) FeCl₃
Answer
(C) — Na⁺ and Cl⁻ are spectator ions from strong acid/base.
17. Which of the following ions would have the smallest radius?
(A) F⁻
(B) O²⁻
(C) Na⁺
(D) Mg²⁺
Answer
(D) — Higher nuclear charge and fewer electrons = smaller ionic radius.
18. Predict the precipitate when solutions of Pb(NO₃)₂ and NaI are mixed.
(A) PbI₂
(B) NaNO₃
(C) NaI
(D) No reaction
Answer
(A) — PbI₂ is insoluble and forms a yellow precipitate.
19. Which polyatomic ion is present in Na₂SO₄?
(A) Sulfite
(B) Sulfate
(C) Thiosulfate
(D) Sulfide
Answer
(B) — SO₄²⁻ is the sulfate ion.
20. Which of the following combinations is most likely to form an insoluble compound?
(A) Na⁺ and NO₃⁻
(B) K⁺ and Cl⁻
(C) Ba²⁺ and SO₄²⁻
(D) NH₄⁺ and I⁻
Answer
(C) — BaSO₄ is a classic example of a low-solubility ionic compound.
21. A student mistakenly wrote the formula for aluminum sulfide as AlS. What is the error?
(A) Aluminum doesn't form ionic bonds
(B) Sulfur must be polyatomic
(C) Charges are not balanced
(D) It's a covalent compound
Answer
(C) — Al³⁺ and S²⁻ require a 2:3 ratio to balance charges → Al₂S₃.
22. Which ionic compound would you expect to be most soluble in water?
(A) AgCl
(B) BaSO₄
(C) NaNO₃
(D) PbI₂
Answer
(C) — Na⁺ and NO₃⁻ both produce highly soluble salts.
23. Which of the following correctly represents the dissociation of K₂SO₄ in water?
(A) K₂SO₄ → K + SO₄
(B) K₂SO₄ → 2K⁺ + SO₄²⁻
(C) K₂SO₄ → K⁺ + 2SO₄²⁻
(D) K₂SO₄ → K⁺ + SO₄²⁺
Answer
(B) — Two potassium ions and one sulfate ion are formed.
24. Which is the correct balanced net ionic equation for: Na₂CO₃ + CaCl₂ → ?
(A) Na⁺ + CO₃²⁻ + Ca²⁺ + Cl⁻ → CaCO₃(s) + NaCl
(B) CO₃²⁻ + Ca²⁺ → CaCO₃(s)
(C) Na₂CO₃ + CaCl₂ → CaCO₃ + NaCl
(D) Ca²⁺ + Cl⁻ → CaCl₂
Answer
(B) — Only ions forming the solid are shown in the net ionic equation.
25. Which ion pair would produce a compound with the greatest lattice energy?
(A) Li⁺ and Cl⁻
(B) Mg²⁺ and O²⁻
(C) Na⁺ and Br⁻
(D) K⁺ and I⁻
Answer
(B) — Smaller, highly charged ions create stronger ionic bonds.
36. Write the chemical formula for cobalt(III) nitrite.
Answer
Co(NO₂)₃ — Cobalt(III) = Co³⁺, Nitrite = NO₂⁻, combined in 1:3 ratio.
37. What is the name of Cr₂(SO₄)₃?
Answer
Chromium(III) sulfate — Cr has a +3 charge to balance SO₄²⁻.
38. Predict the product and state if a precipitate forms: Na₂CO₃ + MgCl₂ → ?
Answer
MgCO₃(s) — Magnesium carbonate precipitates out; net ionic: Mg²⁺ + CO₃²⁻ → MgCO₃(s).
39. Give the formula of the ionic compound formed between Sn⁴⁺ and OH⁻.
Answer
Sn(OH)₄ — Four OH⁻ ions are needed to balance Sn⁴⁺.
40. Name the compound with the formula Ni(CN)₂.
Answer
Nickel(II) cyanide — Ni²⁺ with two cyanide ions (CN⁻).
41. Provide the net ionic equation for: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
Answer
H⁺(aq) + OH⁻(aq) → H₂O(l) — Only participating ions in the reaction are shown.
42. Write the formula for tin(II) phosphate.
Answer
Sn₃(PO₄)₂ — Two PO₄³⁻ ions need three Sn²⁺ to balance.
43. What is the oxidation state of sulfur in Na₂SO₄?
Answer
+6 — Oxygen is –8 total, Na is +2, so sulfur must be +6.
44. Name the compound Fe(ClO₄)₃.
Answer
Iron(III) perchlorate — Fe³⁺ with three ClO₄⁻ ions.
45. Write the ionic formula for the compound formed between Ba²⁺ and CrO₄²⁻.
Answer
BaCrO₄ — The charges are already balanced in a 1:1 ratio.
46. Provide the correct name for Hg₂SO₄.
Answer
Mercury(I) sulfate — Hg₂²⁺ is the mercury(I) ion.
47. Write the chemical formula for lithium oxalate.
Answer
Li₂C₂O₄ — Two Li⁺ ions balance the oxalate ion (C₂O₄²⁻).
48. Predict the precipitate: K₂CrO₄(aq) + Pb(NO₃)₂(aq) → ?
Answer
PbCrO₄(s) — Lead(II) chromate is insoluble in water.
49. What is the correct name of Al(ClO₂)₃?
Answer
Aluminum chlorite — Al³⁺ with three ClO₂⁻ ions.
50. Write the net ionic equation for: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
Answer
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) — This is a single replacement redox reaction.