CBSE Class 10 Science 2020 · Paper 31/5/3 · Question 15

(a) Displacement reaction: aluminium, being more reactive than iron, displaces iron from iron(III) oxide. (It is also a redox reaction, since aluminium is oxidised and ${\text{Fe}}_2{\text{O}}_3$ is reduced, and an exothermic reaction, since heat is given out; it is the thermit reaction.) (b) Double displacement reaction: the two compounds exchange their ions, ${\text{Pb}}^{2+}$ pairing with ${\text{I}}^{-}$ and ${\text{K}}^{+}$ with ${\text{NO}}_3^{-}$; the insoluble yellow ${\text{PbI}}_2$ precipitates, so it is also a precipitation reaction. (c) Decomposition reaction (thermal decomposition, or calcination): a single reactant, zinc carbonate, breaks down on heating into two simpler products, $\text{ZnO}$ and ${\text{CO}}_2$.