Chemistry · May / June 2023 · Paper 12 · Question 27

The table shows some properties of transition elements and the reasons why they have these properties. Which row shows a correct property and the reason why transition elements show this property?

1. Airon has two common oxidation states (I) and (II) / iron atoms can lose one or two electrons to form compounds
2. Bnickel can be used as a catalyst / the use of nickel raises the activation energy of the reaction
3. Cthe reaction of aqueous sodium hydroxide with the salt of a transition element can be used to identify the element / transition metal hydroxides are often coloured
4. Dtransition elements have high melting points / the presence of varying numbers of electrons in the ‘sea’ of delocalised electrons weakens the metallic lattice

As printed in the paper