Variable oxidation states and redox titrations Quiz
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5 questions, one answer each
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1. Which vanadium species is green?
- A. VO₂⁺
- B. VO²⁺
- C. V³⁺
- D. V²⁺
2. Which compound gives a silver mirror when warmed with Tollens' reagent?
- A. Ethanal
- B. Propanone
- C. Pentan-3-one
- D. Propan-2-ol
3. What volume of 0.0200 mol dm⁻³ KMnO₄ reacts with 25.0 cm³ of 0.100 mol dm⁻³ Fe²⁺ in acid?
- A. 125 cm³
- B. 5.00 cm³
- C. 12.5 cm³
- D. 25.0 cm³
4. Why is dilute sulfuric acid, and not hydrochloric acid, used in manganate(VII) titrations?
- A. Sulfuric acid is a stronger acid
- B. MnO₄⁻ would oxidise chloride ions, giving a titre that is too large
- C. Hydrochloric acid reduces Mn²⁺
- D. Sulfuric acid makes the end-point colourless
5. Why is [Co(NH₃)₆]²⁺ oxidised by air but [Co(H₂O)₆]²⁺ is not?
- A. Ammonia is a stronger acid than water
- B. Ammonia raises E° for Co³⁺/Co²⁺
- C. Ammonia ligands stabilise Co(III), lowering E°
- D. Water ligands are bidentate