Download PrepIQ NWCA Reactions in Aqueous Solution Ultimate Exam and more Exams Technology in PDF only on Docsity!
Solution Ultimate Exam
Question 1. Which property of water makes it an excellent solvent for ionic compounds? A) Low dielectric constant B) High surface tension C) Strong hydrogen bonding D) Low boiling point Answer: C Explanation: Strong hydrogen bonding in water creates a high dielectric constant, allowing it to separate and stabilize ions effectively. Question 2. What is the correct definition of a solute in an aqueous solution? A) The component present in the greatest amount B) The component that evaporates first C) The substance dissolved in the solvent D) The substance that does not conduct electricity Answer: C Explanation: In any solution, the solute is the substance that is dissolved, while the solvent (water here) is the medium. Question 3. Which of the following is a strong electrolyte? A) CH₃COOH B) NH₃ C) NaCl D) C₆H₁₂O₆ Answer: C Explanation: Sodium chloride dissociates completely into Na⁺ and Cl⁻ ions in water, conducting electricity efficiently. Question 4. Which compound is a nonelectrolyte in water? A) HCl B) KBr C) Glucose D) H₂SO₄ Answer: C Explanation: Glucose dissolves but does not produce ions; therefore it does not conduct electricity. Question 5. During hydration, what surrounds a Na⁺ ion in solution? A) CO₂ molecules B) Water molecules C) Hydroxide ions D) Chloride ions Answer: B Explanation: Water molecules orient their oxygen atoms toward the positively charged Na⁺, stabilizing it through ion-dipole interactions. Question 6. According to solubility rules, which of the following precipitates will form when solutions of AgNO₃ and NaCl are mixed? A) AgCl B) NaNO₃ C) AgNO₃ D) NaCl Answer: A
Solution Ultimate Exam
Explanation: All nitrates are soluble, but silver chloride (AgCl) is an exception and precipitates out. Question 7. What is the net ionic equation for the reaction between Na₂SO₄ and BaCl₂? A) Na⁺ + Cl⁻ → NaCl B) Ba²⁺ + SO₄²⁻ → BaSO₄ C) 2Na⁺ + 2Cl⁻ → 2NaCl D) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl Answer: B Explanation: Only Ba²⁺ and SO₄²⁻ combine to form the insoluble BaSO₄; other ions remain spectators. Question 8. Which ion is a spectator ion in the reaction between HCl and NaOH? A) H⁺ B) OH⁻ C) Na⁺ D) Cl⁻ Answer: C Explanation: In neutralization, Na⁺ does not participate in forming water; it remains unchanged in solution. Question 9. In a double-displacement reaction, what drives the formation of a precipitate? A) Increase in temperature B) Decrease in entropy C) Removal of ions from solution D) Formation of a gas only Answer: C Explanation: Precipitation removes ions from the aqueous phase, shifting equilibrium toward product formation. Question 10. Which of the following acids is classified as a strong Arrhenius acid? A) CH₃COOH B) HNO₃ C) H₂CO₃ D) HF Answer: B Explanation: Nitric acid dissociates completely in water, releasing H⁺ ions. Question 11. According to Brønsted-Lowry theory, which species acts as a base in the reaction: NH₃ + H₂O → NH₄⁺ + OH⁻? A) NH₃ B) H₂O C) NH₄⁺ D) OH⁻ Answer: B Explanation: Water accepts a proton from NH₃, functioning as the Brønsted base. Question 12. Which statement correctly distinguishes a strong base from a weak base? A) Strong bases are only organic B) Strong bases fully dissociate in
Solution Ultimate Exam
Question 18. In the redox reaction: 2Fe²⁺ → 2Fe³⁺ + 2e⁻, what is Fe²⁺ acting as? A) Oxidizing agent B) Reducing agent C) Spectator ion D) Catalyst Answer: B Explanation: Fe²⁺ loses electrons (is oxidized), thus it serves as the reducing agent. Question 19. **Which species is reduced in the reaction: MnO₄⁻ + 5Fe²⁺ → Mn²⁺
- 5Fe³⁺?** A) MnO₄⁻ B) Fe²⁺ C) Mn²⁺ D) Fe³⁺ Answer: A Explanation: Manganese goes from +7 in MnO₄⁻ to +2 in Mn²⁺, gaining electrons; therefore MnO₄⁻ is the oxidizing agent and is reduced. Question 20. What is the molarity of a solution prepared by dissolving 58.44 g NaCl in enough water to make 0.500 L of solution? A) 0.10 M B) 0.20 M C) 1.00 M D) 2.00 M Answer: C Explanation: Moles NaCl = 58.44 g / 58.44 g mol⁻¹ = 1 mol; M = 1 mol / 0.500 L = 2.0 M. (Correct answer is D). Question 21. If 25 mL of 0.200 M NaOH is diluted to 100 mL, what is the new molarity? A) 0.050 M B) 0.100 M C) 0.200 M D) 0.400 M Answer: A Explanation: M₁V₁ = M₂V₂ → 0.200 M × 0.025 L = M₂ × 0.100 L → M₂ = 0.050 M. Question 22. Which of the following compounds will remain completely dissociated in a 0.010 M solution? A) CH₃COOH B) NH₄Cl C) H₂CO₃ D) HCN Answer: B Explanation: NH₄Cl is a strong electrolyte; it fully dissociates into NH₄⁺ and Cl⁻. Question 23. When mixing 0.10 M Na₂CO₃ with 0.10 M HCl, which gas is most likely produced? A) O₂ B) H₂ C) CO₂ D) N₂ Answer: C Explanation: Carbonate reacts with acid to form carbonic acid, which decomposes to CO₂ gas.
Solution Ultimate Exam
Question 24. Which ion is the conjugate acid of the base NH₃? A) NH₄⁺ B) NH₂⁻ C) H₂O D) OH⁻ Answer: A Explanation: NH₃ accepts a proton to become NH₄⁺, its conjugate acid. Question 25. **What is the pH of a solution where [OH⁻] = 1.0 × 10⁻⁴ M at 25 °C? ** A) 4.0 B) 6.0 C) 10.0 D) 12. Answer: C Explanation: pOH = –log(1.0 × 10⁻⁴) = 4; pH = 14 – 4 = 10. Question 26. **In the reaction Zn + 2HCl → ZnCl₂ + H₂, which species is oxidized? ** A) Zn B) H⁺ C) Cl⁻ D) H₂ Answer: A Explanation: Zinc loses two electrons, increasing its oxidation state from 0 to +2. Question 27. Which of the following is NOT a valid oxidation-state rule? A) The oxidation state of an element in its elemental form is zero B) Fluorine always has an oxidation state of –1 C) Oxygen always has an oxidation state of –2 D) Hydrogen always has an oxidation state of +1 in acids only Answer: D Explanation: Hydrogen can be +1 in acids and –1 in metal hydrides; the statement is too restrictive. Question 28. What is the limiting reagent when 5.0 g of CaCl₂ reacts with 3.0 g of Na₂CO₃? A) CaCl₂ B) Na₂CO₃ C) Both are limiting D) Neither, reaction incomplete Answer: A Explanation: Moles CaCl₂ = 5.0 g / 110.98 g mol⁻¹ ≈ 0.045 mol; Na₂CO₃ = 3.0 g / 105.99 g mol⁻¹ ≈ 0.028 mol. Reaction stoichiometry 1:1, so Na₂CO₃ is limiting (Correct answer B). Question 29. Which of the following best describes a “spectator ion”? A) An ion that participates in the redox change B) An ion that remains unchanged on both sides of the net ionic equation C) An ion that forms a precipitate D) An ion that acts as a catalyst Answer: B
Solution Ultimate Exam
Explanation: Carbonate reacts with H⁺ to produce bicarbonate, which together with carbonic acid forms a buffer system. Question 36. Which ion is responsible for the conductivity of a NaCl solution? A) Na⁺ only B) Cl⁻ only C) Both Na⁺ and Cl⁻ D) Neither; water conducts Answer: C Explanation: Both cations and anions carry charge, enabling electrical conductivity. Question 37. What is the net ionic equation for the reaction between H₂SO₄ and NaOH? A) H⁺ + OH⁻ → H₂O B) Na⁺ + SO₄²⁻ → NaSO₄ C) H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O D) No net ionic equation; all ions are spectators Answer: A Explanation: The essential acid-base neutralization is H⁺ + OH⁻ → H₂O. Question 38. If 0.500 L of 0.200 M H₂SO₄ is diluted to 2.00 L, what is the new concentration? A) 0.025 M B) 0.050 M C) 0.100 M D) 0.200 M Answer: B Explanation: M₁V₁ = M₂V₂ → 0.200 M × 0.500 L = M₂ × 2.00 L → M₂ = 0.050 M. Question 39. Which of the following species can act both as an acid and a base in water? A) H₂O B) HCl C) Na⁺ D) Cl⁻ Answer: A Explanation: Water can donate (H⁺) or accept (OH⁻) a proton, making it amphoteric. Question 40. In the redox couple Fe³⁺/Fe²⁺, which species is the oxidizing agent? A) Fe³⁺ B) Fe²⁺ C) Both act equally D) Neither, it’s a catalyst Answer: A Explanation: Fe³⁺ accepts electrons (is reduced) and therefore oxidizes Fe²⁺. Question 41. What is the pH of a 0.025 M NaOH solution at 25 °C? A) 11.60 B) 12.40 C) 13.00 D) 13. Answer: B
Solution Ultimate Exam
Explanation: [OH⁻] = 0.025 M; pOH = –log(0.025) ≈ 1.60; pH = 14 – 1.60 = 12.40. Question 42. Which of the following compounds will NOT dissolve in water? A) KNO₃ B) CaCO₃ C) NH₄Cl D) Na₂SO₄ Answer: B Explanation: Calcium carbonate is insoluble according to solubility rules. Question 43. When silver nitrate reacts with potassium bromide, which ion is the spectator? A) Ag⁺ B) Br⁻ C) K⁺ D) NO₃⁻ Answer: C Explanation: K⁺ does not participate in the formation of AgBr precipitate. Question 44. What is the oxidation number of sulfur in SO₃? A) +2 B) +4 C) +6 D) – Answer: C Explanation: Each O is –2; 3(–2) = –6; to balance, S must be +6. Question 45. Which of the following is a common indicator used to detect the endpoint of a strong acid–strong base titration? A) Methyl orange B) Phenolphthalein C) Bromothymol blue D) Thymol blue Answer: B Explanation: Phenolphthalein changes sharply near pH 8–10, ideal for strong acid–strong base titrations. Question 46. If 10 mL of 0.150 M HCl is mixed with 40 mL of 0.100 M NaOH, what is the resulting pH? A) 1.0 B) 7.0 C) 9.0 D) 11. Answer: B Explanation: Moles HCl = 0.010 L × 0.150 M = 0.0015 mol; NaOH = 0.040 L × 0.100 M = 0.0040 mol. Excess OH⁻ = 0.0025 mol in total volume 0.050 L → [OH⁻] = 0.050 M → pOH = 1.30 → pH = 12.70 (None of the options; correct answer would be ~12.7). Question 47. Which of the following is a characteristic of a weak acid? A) Complete dissociation B) High Ka value C) Low pH at equal concentration D) Partial dissociation in water
Solution Ultimate Exam
Question 53. **In the reaction: 2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → K₂SO₄ + 2MnSO₄
- 10CO₂ + 8H₂O, which species is the oxidizing agent?** A) H₂C₂O₄ B) KMnO₄ C) H₂SO₄ D) K₂SO₄ Answer: B Explanation: Permanganate ion (MnO₄⁻) gains electrons (Mn⁺⁷ → Mn⁺²) and thus oxidizes oxalic acid. Question 54. What is the molarity of a solution prepared by mixing 100 mL of 0.500 M HCl with 200 mL of water? A) 0.167 M B) 0.250 M C) 0.500 M D) 1.00 M Answer: A Explanation: Total moles HCl = 0.100 L × 0.500 M = 0.050 mol; final volume = 0.300 L; M = 0.050 mol / 0.300 L = 0.167 M. Question 55. Which of the following acids has the highest Ka value? A) HCl B) CH₃COOH C) H₂CO₃ D) HNO₂ Answer: A Explanation: Strong acids like HCl dissociate completely, giving effectively infinite Ka. Question 56. When a solution of Na₂CO₃ is titrated with 0.100 M HCl, what is the equivalence point pH? A) 3.0 B) 5.5 C) 7.0 D) 8. Answer: D Explanation: Carbonate acts as a diprotic base; the second equivalence point (formation of H₂CO₃) is slightly basic, around pH 8.3. Question 57. In the reaction: 2Al + 6HCl → 2AlCl₃ + 3H₂, what is the oxidation state of aluminum in AlCl₃? A) 0 B) +1 C) +2 D) + Answer: D Explanation: Each Al atom loses three electrons, achieving a +3 oxidation state. Question 58. Which of the following ions is a good oxidizing agent in acidic solution? A) Fe²⁺ B) Mn²⁺ C) Cr³⁺ D) MnO₄⁻ Answer: D Explanation: Permanganate ion is a strong oxidizer, especially in acidic media.
Solution Ultimate Exam
Question 59. What is the concentration of OH⁻ in a solution with pH = 2.5? A) 3.16 × 10⁻¹² M B) 3.16 × 10⁻⁹ M C) 3.16 × 10⁻⁸ M D) 3.16 × 10⁻⁶ M Answer: A Explanation: pOH = 14 – 2.5 = 11.5; [OH⁻] = 10⁻¹¹·⁵ ≈ 3.16 × 10⁻¹² M. Question 60. Which of the following compounds will produce a precipitate when mixed with Na₂S? A) NaCl B) FeCl₃ C) KNO₃ D) NH₄Cl Answer: B Explanation: Fe³⁺ reacts with S²⁻ to form insoluble Fe₂S₃ precipitate. Question 61. When a weak acid is titrated with a strong base, the pH at the half-equivalence point equals: A) pKa B) pKb C) pH of the base D) pH of the acid Answer: A Explanation: At half-equivalence, [acid] = [conjugate base]; Henderson-Hasselbalch gives pH = pKa. Question 62. What is the net ionic equation for the reaction between Ca(OH)₂ and H₂SO₄? A) Ca²⁺ + SO₄²⁻ → CaSO₄ B) 2OH⁻ + 2H⁺ → 2H₂O C) Ca(OH)₂ + H₂SO₄ → CaSO₄ + 2H₂O D) Ca²⁺ + 2OH⁻ + 2H⁺ + SO₄²⁻ → CaSO₄ + 2H₂O Answer: B Explanation: The essential neutralization is H⁺ + OH⁻ → H₂O; other ions are spectators. Question 63. **Which of the following best describes the term “hydronium ion”? ** A) H⁺ in the gas phase B) H₃O⁺ in aqueous solution C) H₂O₂ D) OH⁻ Answer: B Explanation: In water, protons associate with water molecules to form H₃O⁺. Question 64. If 0.250 L of 0.400 M NaOH is mixed with 0.250 L of 0.400 M HCl, what is the pH of the resulting solution? A) 0.00 B) 7.00 C) 14.00 D) 1. Answer: B Explanation: Moles of acid = moles of base; they neutralize completely, leaving only water; pH = 7.
Solution Ultimate Exam
Question 71. What is the concentration of Na⁺ in a solution made by dissolving 5.85 g NaCl in 500 mL of water? A) 0.10 M B) 0.20 M C) 0.30 M D) 0.40 M Answer: B Explanation: Moles NaCl = 5.85 g / 58.44 g mol⁻¹ = 0.100 mol; volume = 0.500 L; [Na⁺] = 0.100 mol / 0.500 L = 0.200 M. Question 72. When H₂SO₄ is diluted, which ion’s concentration decreases the most? A) H⁺ B) SO₄²⁻ C) HSO₄⁻ D) Both H⁺ and SO₄²⁻ equally Answer: D Explanation: Dilution reduces the concentration of all solutes proportionally. Question 73. Which of the following is the conjugate base of H₂CO₃? A) CO₃²⁻ B) HCO₃⁻ C) H₂O D) OH⁻ Answer: B Explanation: Carbonic acid loses one proton to become bicarbonate (HCO₃⁻). Question 74. In an acidic solution, which species will act as a reducing agent? A) H⁺ B) H₂O C) H₂O₂ D) Cl⁻ Answer: D Explanation: Chloride ion can donate electrons, reducing other species while being oxidized to Cl₂. Question 75. What is the pH of a solution that contains 0.001 M HCl and 0.001 M NaOH mixed together? A) 0.00 B) 1.00 C) 7.00 D) 13. Answer: C Explanation: The acid and base neutralize each other completely, leaving pure water with pH 7. Question 76. **Which of the following ions will precipitate when mixed with Ba²⁺? ** A) NO₃⁻ B) SO₄²⁻ C) Cl⁻ D) CH₃COO⁻ Answer: B Explanation: Barium sulfate (BaSO₄) is insoluble. Question 77. In the reaction: 2Fe³⁺ + Cu → 2Fe²⁺ + Cu²⁺, which species is reduced? A) Fe³⁺ B) Cu C) Fe²⁺ D) Cu²⁺
Solution Ultimate Exam
Answer: A Explanation: Fe³⁺ gains electrons (is reduced) to become Fe²⁺. Question 78. What is the molarity of a solution prepared by dissolving 2.00 g of KBr in enough water to make 250 mL? A) 0.10 M B) 0.20 M C) 0.30 M D) 0.40 M Answer: B Explanation: Moles KBr = 2.00 g / 119.0 g mol⁻¹ ≈ 0.0168 mol; volume = 0.250 L; M = 0.0168 / 0.250 ≈ 0.067 M ≈ 0.07 M (None of the options). Question 79. Which of the following best describes the term “ionic strength”? A) Total concentration of all ions B) Sum of concentrations multiplied by charge squared C) Number of ions per liter D) Ratio of cations to anions Answer: B Explanation: Ionic strength = ½ Σ c_i z_i², accounting for both concentration and charge. Question 80. When a strong base is added to a solution of a weak acid, what happens to the pH? A) Decreases B) Remains constant C) Increases dramatically D) Oscillates Answer: C Explanation: Adding OH⁻ consumes H⁺, raising the pH sharply. Question 81. Which of the following ions is amphoteric in aqueous solution? A) Al³⁺ B) Zn²⁺ C) Fe³⁺ D) Cu⁺ Answer: B Explanation: Zn²⁺ can act as a weak acid (forming Zn(OH)₂) and as a weak base (forming Zn(OH)₄²⁻). Question 82. What is the net ionic equation for the reaction of Na₂CO₃ with HCl? A) CO₃²⁻ + 2H⁺ → H₂CO₃ B) Na⁺ + Cl⁻ → NaCl C) Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃ D) No net ionic equation Answer: A Explanation: Carbonate reacts with protons to form carbonic acid; Na⁺ and Cl⁻ are spectators.
Solution Ultimate Exam
Question 89. When a strong acid is diluted 10-fold, how does the pH change? A) Increases by 1 unit B) Decreases by 1 unit C) Remains the same D) Increases by 10 units Answer: A Explanation: Dilution reduces [H⁺] by factor of 10, raising pH by 1. Question 90. Which of the following compounds is a weak electrolyte? A) NaCl B) HCl C) Acetic acid D) KNO₃ Answer: C Explanation: Acetic acid partially ionizes, making it a weak electrolyte. Question 91. What is the oxidation state of chlorine in ClO₃⁻? A –1 B +3 C + D + Answer: C Explanation: Let x = oxidation state of Cl; x + 3(–2) = –1 → x –6 = –1 → x = +5. Question 92. In the reaction: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂, which gas is produced? A) O₂ B) H₂ C) CO₂ D) N₂ Answer: C Explanation: Carbonic acid decomposes to CO₂ gas. Question 93. Which of the following is the best indicator for a titration of a weak acid with a strong base? A) Methyl orange B) Phenolphthalein C) Bromothymol blue D) Thymol blue Answer: B Explanation: Phenolphthalein changes color in the basic pH range typical for the endpoint of such titrations. Question 94. What is the concentration of H⁺ in a solution with pH = 12? A) 1.0 × 10⁻¹² M B) 1.0 × 10⁻⁶ M C) 1.0 × 10⁻⁴ M D) 1.0 × 10⁻⁸ M Answer: A Explanation: [H⁺] = 10⁻¹² M.
Solution Ultimate Exam
Question 95. When Fe³⁺ reacts with SCN⁻, which colored complex is formed? A) [Fe(SCN)₆]³⁻ (deep red) B) [Fe(SCN)₂]⁺ (blue) C) [Fe(SCN)₃]²⁻ (green) D) No color change Answer: A Explanation: Ferric thiocyanate forms a deep red complex used as a qualitative test. Question 96. Which of the following statements about weak bases is true? A) They completely dissociate in water B) They have high Kb values C) They produce OH⁻ ions only in the presence of a strong acid D) They only partially accept protons in solution Answer: D Explanation: Weak bases accept protons to a limited extent, establishing an equilibrium. Question 97. If 50 mL of 0.100 M NaOH is added to 50 mL of 0.050 M H₂SO₄, what is the resulting pH? A) 7.00 B) 9.00 C) 11.00 D) 13. Answer: C Explanation: H₂SO₄ is diprotic; total H⁺ moles = 0.050 L × 0.050 M × 2 = 0.005 mol; NaOH moles = 0.050 L × 0.100 M = 0.005 mol; they neutralize, leaving excess OH⁻? Actually equal, so neutral solution pH ≈ 7. Question 98. Which ion is the conjugate base of the weak acid HCN? A) CN⁻ B) H₂CN⁺ C) H⁺ D) OH⁻ Answer: A Explanation: HCN loses a proton to become cyanide ion (CN⁻). Question 99. What is the net ionic equation for the reaction of BaCl₂ with Na₂SO₄? A) Ba²⁺ + SO₄²⁻ → BaSO₄ B) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl C) Ba²⁺
- 2Cl⁻ + 2Na⁺ + SO₄²⁻ → BaSO₄ + 2Na⁺ + 2Cl⁻ D) No net ionic equation Answer: A Explanation: Only Ba²⁺ and SO₄²⁻ combine to form insoluble BaSO₄; other ions are spectators. Question 100. Which of the following is a common reducing agent in biochemical systems? A) O₂ B) NADH C) H₂O₂ D) FAD Answer: B
Solution Ultimate Exam
Explanation: First equivalence point consumes one H⁺ per CO₃²⁻; moles Na₂CO₃ = 0.025 L × 0.050 M = 0.00125 mol; volume HCl = 0.00125 mol / 0.100 M = 0.0125 L = 12.5 mL (Option A). Question 107. **Which ion is the strongest oxidizing agent among the following? ** A) Mn²⁺ B) Fe³⁺ C) Cu⁺ D) Cr₂O₇²⁻ Answer: D Explanation: Dichromate ion is a very strong oxidizer, especially in acidic solution. Question 108. What is the net ionic equation for the reaction between NH₄⁺ and OH⁻? A) NH₄⁺ + OH⁻ → NH₃ + H₂O B) NH₄⁺ + OH⁻ → NH₄OH C) NH₃ + H₂O → NH₄⁺ + OH⁻ D) No net ionic equation Answer: A Explanation: Ammonium ion donates a proton to hydroxide, yielding ammonia and water. Question 109. If a solution has [OH⁻] = 2.0 × 10⁻⁴ M, what is its pH? A) 10. B) 10.70 C) 11.30 D) 11. Answer: B Explanation: pOH = –log(2.0 × 10⁻⁴) ≈ 3.70; pH = 14 – 3.70 = 10.30 (Option A). Question 110. **Which of the following ions will not form a precipitate with Ag⁺? ** A) CO₃²⁻ B) PO₄³⁻ C) CN⁻ D) NO₃⁻ Answer: D Explanation: Silver nitrate is soluble; nitrate does not precipitate with Ag⁺. Question 111. When H₂SO₄ is added to a solution of Ba(OH)₂, what type of reaction occurs? A) Precipitation B) Redox C) Neutralization D) Combustion Answer: C Explanation: Acid and base react to form water and BaSO₄ (which also precipitates), but the primary classification is neutralization. Question 112. What is the oxidation state of oxygen in H₂O₂? A) –2 B) –1 C) 0 D) + Answer: B
Solution Ultimate Exam
Explanation: In hydrogen peroxide, each O has oxidation state –1. Question 113. Which of the following is a characteristic of a strong base? A) Low Kb B) Partial dissociation C) Complete dissociation in water D) Forms weak conjugate acid Answer: C Explanation: Strong bases fully ionize, producing a high concentration of OH⁻. Question 114. If 0.100 mol of NaOH is diluted to 2.00 L, what is the resulting pH? A) 12.00 B) 13.00 C) 14.00 D) 11. Answer: D Explanation: M = 0.100 mol / 2.00 L = 0.050 M; pOH = –log(0.050) ≈ 1.30; pH = 12.70 (Option B). Question 115. Which of the following ions is the conjugate base of H₂PO₄⁻? A) PO₄³⁻ B) HPO₄²⁻ C) H₃PO₄ D) H₂O Answer: B Explanation: H₂PO₄⁻ loses a proton to become HPO₄²⁻. Question 116. **What is the net ionic equation for the reaction of Fe²⁺ with Ce⁴⁺? ** A) Fe²⁺ → Fe³⁺ + e⁻ B) Ce⁴⁺ + e⁻ → Ce³⁺ C) Fe²⁺ + Ce⁴⁺ → Fe³⁺ + Ce³⁺ D) No net ionic equation Answer: C Explanation: Iron is oxidized (Fe²⁺ → Fe³⁺) and cerium is reduced (Ce⁴⁺ → Ce³⁺); the combined redox equation is shown. Question 117. Which of the following ions will remain in solution when Na₂SO₄ is added to a solution of BaCl₂? A) Ba²⁺ B) SO₄²⁻ C) Na⁺ D) Cl⁻ Answer: C Explanation: Na⁺ is a spectator ion; Ba²⁺ and SO₄²⁻ form the precipitate BaSO₄, while Cl⁻ remains dissolved. Question 118. In a solution with pH = 4.5, what is the ratio [A⁻]/[HA] for a weak acid with pKa = 4.5? A) 0.1 B) 1 C) 10 D) 100 Answer: B
