Answer: The correct answer is Option b.
Explanation:
Double displacement reactions are defined as the reactions in which exchange of ions takes place.
[tex]AB+CD\rightarrow CB+AD[/tex]
For the given options:
Option a: [tex]3Fe+2O_2\rightarrow Fe_3O_4[/tex]
This is an example of synthesis reaction.
Option b: [tex]BaCl_2+K_2CO_3\rightarrow BaCO_3+2KCl[/tex]
This is an example of double displacement reaction.
Option c: [tex]NiCO_3\rightarrow NiO+CO_2[/tex]
This is an example of decomposition reaction.
Option d: [tex]Cl_2+2NaBr\rightarrow 2NaCl+Br_2[/tex]
This is an example of single displacement reaction.
From the above information, the correct answer is Option b.
