IMAT 2012 Q67 [Chemical Reactions]

Consider the following reactions.

{C_2H_5Br + OH­^- → C_2H_5OH + Br^-}

{Ba^{2+}(aq) + SO4^{2-}→ BaSO_4(s)}

{Mg(s) + Cu^{2+}(aq) → Mg^{2+}(aq) + Cu(s)}

Which one of the following types of reaction is NOT included in this list?

A. substitution
B. oxidation/reduction
C. displacement
D. precipitation
E. elimination


The first reaction is both a displacement and substitution reaction. Bromine has been displaced or substituted by the hydroxyl group. Therefore, we can eliminate A and C.

The second reaction is what is called a precipitation reaction. You should remember that Barium Sulphate is insoluble- and to form it, it would require a precipitation reaction. We can eliminate D.

The last reaction is a redox reaction, we can clearly see the change in oxidation states of each reactant. Therefore we can eliminate B.

We have not seen any elimination reactions, and so our answer is E.