Chemistry 9701 · AS & A Level · Electrochemistry

Electrochemistry — practice question

The reaction equation for aqueous thiosulfate ions, $\text{S}_2\text{O}_3^{2-}$, reacting with aqueous dioxo-vanadium ions, $\text{VO}_2^+$, is given below. $2\text{S}_2\text{O}_3^{2-} + x\text{VO}_2^+ + y\text{H}^+ \rightarrow \text{S}_4\text{O}_6^{2-} + z\text{VO}^{2+} + 2\text{H}_2\text{O}$. Which row gives two statements that are both correct for this reaction equation?

  • A$x$ and $z$ are the same value and quarter the value of $y$; change in oxidation number of vanadium from $+4$ to $+5$
  • B$x$ and $z$ are the same value and quarter the value of $y$; change in oxidation number of vanadium from $+5$ to $+4$
  • C$x$ and $z$ are the same value and half the value of $y$; change in oxidation number of vanadium from $+5$ to $+4$
  • D$x$ and $z$ are the same value and half the value of $y$; change in oxidation number of vanadium from $+4$ to $+5$

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