Question

Which of the following is an example of a double displacement reaction?

• A. ${\text{CO}}_2\text{(g)}+{\text{H}}_2\text{(g)}\to \text{CO(g)}+{\text{H}}_2\text{O (g)}$
• B. ${\text{P}}_4{\text{O}}_{10}\text{(s)}+6{\text{H}}_2\text{O(l)}\to 4{\text{H}}_3{\text{PO}}_4\text{(aq)}$
• C. ${\text{H}}_2\text{(g)}+{\text{O}}_2\text{(g)}\to {\text{H}}_2\text{O}\text{(l)}$
• D. ${\text{CoCl}}_2\text{(aq)}+{\text{Na}}_2{\text{CO}}_3\text{(aq)}\to {\text{CoCO}}_3\text{(aq)}+2\text{NaCl(aq)}$

Answer 1

The correct option is D ${\text{CoCl}}_2\text{(aq)}+{\text{Na}}_2{\text{CO}}_3\text{(aq)}\to {\text{CoCO}}_3\text{(aq)}+2\text{NaCl(aq)}$

In a double displacement reaction, the positive ions (cations) and the negative ions (anions) of the two reactants switch places, forming two new compounds or products.

In the reaction between cobalt chloride and sodium carbonate, the anions ${\text{Cl}}^{-}$ and ${\text{CO}}_3^{2-}$swap their places and form cobalt carbonate and sodium chloride. Hence it is an example of a double displacement reaction.