Question

Which of the following are combination reactions?

1. \[\ce{2KClO3 -> 2KCl + 3O2}\]
2. \[\ce{MgO + H2O -> Mg(OH)2}\]
3. \[\ce{4Al + 3O2 -> 2Al2O3}\]
4. \[\ce{Zn + FeSO4 -> ZnSO4 + Fe}\]

Options

• (i) and (iii)

• (iii) and (iv)

• (ii) and (iv)

• (ii) and (iii)

Answer 1

(ii) and (iii)

Explanation:

A combination reaction is one in which two or more substances combine to form a single product.
\[\ce{MgO + H2O -> Mg(OH)2}\] and \[\ce{4Al + 3O2 -> 2Al2O3}\] form single products, so they are combination reactions. The others are decomposition (i) and displacement (iv) reactions.