CAIE IGCSE Chemistry 8.4 Transition Elements Topic Practice

Hydrogen iodide thermally decomposes into iodine and hydrogen. The reaction is reversible.

Fig. 4.1 shows a gas syringe containing a mixture of hydrogen iodide, iodine and hydrogen gases. The gas syringe is sealed and the mixture is heated to $300^{\circ} \mathrm{C}$. The mixture of gases reaches equilibrium and is purple.

Methanol is manufactured by reacting carbon monoxide with hydrogen.

The rate of formation of methanol increases when a catalyst is used.

Choose from the list the element that is most likely to be used as the catalyst.

Draw a circle around your chosen answer.
calcium carbon copper sodium sulfur

Which statements about transition elements are correct?

1 They have a low density.
2 They form ions with variable oxidation numbers.
3 They have a high melting point.
4 They form only colourless compounds.