Redox chemistry of vanadium and chromium Quiz
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5 questions, one answer each
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1. Which vanadium species is green?
- A. VO₂⁺
- B. V³⁺
- C. VO²⁺
- D. V²⁺
2. Using E°(Zn²⁺/Zn) = −0.76 V and E°(V³⁺/V²⁺) = −0.26 V, what is E°cell for zinc reducing V³⁺?
- A. +0.50 V
- B. −0.50 V
- C. +1.02 V
- D. −1.02 V
3. What is the colour of the species in which chromium has oxidation number +2?
- A. Orange
- B. Green
- C. Yellow
- D. Blue
4. What happens when aqueous sodium hydroxide is added to an orange solution of dichromate(VI)?
- A. It turns green as Cr³⁺ forms
- B. It turns yellow as the equilibrium shifts towards chromate(VI)
- C. It turns blue as Cr²⁺ forms
- D. There is no change because chromium is in the +6 state in both ions
5. Which conditions oxidise Cr³⁺ to CrO₄²⁻?
- A. Zinc and dilute acid
- B. Iron(II) ions in acid
- C. Hydrogen peroxide in alkaline solution
- D. Dilute acid alone