Chemistry of transition elements — Chemistry 9701 AS & A Level Question & Worked Solution

(a(i))

Suggest why transition elements display variable oxidation states in their compounds whereas s-block elements like calcium do not.

(a(ii))[4]

Calculate the oxidation number of the metal in each of these ions: $\text{VO}_2^{+}$, $\text{CrF}_6^{2-}$, $\text{MnO}_4^{2-}$.

(b)[4]

Explain why complexes of transition elements are often coloured whereas compounds of s-block elements such as calcium and sodium are not.

(c(i))

Use the Data Booklet to build a balanced equation for the reaction of $\text{SO}_2$ and $\text{MnO}_4^{-}$ in acidic solution.

(c(ii))

Describe the colour change you would observe when $\text{SO}_2(\text{aq})$ is added to a sample of acidified $\text{KMnO}_4$ until the $\text{SO}_2$ is in excess.

(d)[3]

Describe the observations you would make when $\text{NH}_3(\text{aq})$ is added drop by drop to a solution containing $\text{Cu}^{2+}$ ions, until the $\text{NH}_3$ is in excess.

Chemistry of transition elements — practice question

Worked solution & mark scheme