Define the term transition element.
State any two further typical chemical properties of transition elements.
Explain why transition elements show variable oxidation states.
In acidic solution, $\text{C}_2\text{O}_4^{2-}$ reduces $\text{VO}_2^+$ to $\text{V}^{2+}$. equation 2 is: $2\text{VO}_2^+ + 3\text{C}_2\text{O}_4^{2-} + 8\text{H}^+ \rightarrow 2\text{V}^{2+} + 6\text{CO}_2 + 4\text{H}_2\text{O}$ In the titration, $25.00\text{ cm}^3$ of $0.0300\text{ mol dm}^{-3}$ $\text{VO}_2^+(aq)$ is measured into $10\text{ cm}^3$ of dilute sulfuric acid. A $0.0400\text{ mol dm}^{-3}$ $\text{C}_2\text{O}_4^{2-}(aq)$ solution is then run from a burette until the end-point is reached. The titration is repeated and concordant values are obtained, as listed in Table 3.1. Show that the results fit the stoichiometry of equation 2.
An excess of $\text{C}_2\text{O}_4^{2-}$ reacts with $\text{VO}_2^+$ to produce a mixture of two octahedral complex ions. These complex ions are stereoisomers of one another. Each complex ion has a $\text{V}^{2+}$ cation and three $\text{C}_2\text{O}_4^{2-}$ ions. Complete the diagram so that it shows the three-dimensional structure of one of the complex ions. State the charge of the complex ion. Use the symbol provided to stand for a $\text{C}_2\text{O}_4^{2-}$ ion.
Identify the vanadium species that is produced when an excess of $\text{H}_2\text{O}_2$(aq) reacts with $\text{V}^{2+}$(aq) under standard conditions. Explain your answer using the data in Table 3.2.
Concentrated acidified $\text{H}_2\text{O}_2$ may react with $\text{V}^{2+}$ to form red $\text{VO}_2^{3+}$ ions. $\text{VO}_2^{3+}$ contains vanadium combined with the peroxide anion, $\text{O}_2^{2-}$. Deduce the oxidation state of vanadium in $\text{VO}_2^{3+}$.