Question

Which of the following is an example of double displacement reaction?
(i) $C{O}_2\left(g\right)+H_2\left(g\right)\to CO\left(g\right)+H_{2}O\left(g\right)$
(ii) $P_4{O}_{10}\left(s\right)+6H_{2}O\left(l\right)\to 4H_{3}P{O}_4\left(aq\right)$​​​​​​​
(iii) $H_2+O_2\to H_{2}O$​​​​​​​
(iv) $CoC{l}_2\left(aq\right)+N{a}_{2}C{O}_3\left(aq\right)\to CoC{O}_3\left(aq\right)+2NaCl\left(aq\right)$​​​​​​​

• A. (i)
• B. (ii)
• C. (iii)
• D. (iv)

Answer 1

The correct option is D (iv)

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 equation,
$CoC{l}_2\left(aq\right)+N{a}_{2}C{O}_3\left(aq\right)\to CoC{O}_3\left(aq\right)+2NaCl\left(aq\right)$
the anions $C{l}^{-}\&C{O}_3^{2-}$ swap their places and form $CoC{O}_3\&2NaCl$, hence it is an example of double displacement reaction.