Respuesta :
Reaction 3 is the double displacement reaction.
Double displacement reaction occurs when the negatively and the positively charged ions of the compounds interchange their position when the new compound in the product is formed.
Which is a double displacement reaction?
In the first reaction, the element lead (Pb) is not an ion and no exchange of the cations or the anions occurs hence it is not a double displacement reaction.
In the second reaction, one compound is getting split into two new compounds and is a decomposition reaction.
In the third reaction, [tex]\rm Br^{-}[/tex] in [tex]\rm 2NaBr[/tex] and [tex]\rm (OH)_{2}[/tex] in [tex]\rm Ca(OH)_{2}[/tex] are anions and cations and exchanges their places to produce two new compounds [tex]\rm CaBr_{2} + 2NaOH.[/tex]
In the fourth reaction, a single compound is generated as the result of the combination reaction and hence, it is not the double displacement reaction.
Therefore, [tex]\rm 2NaBr + Ca(OH)_{2} \rightarrow CaBr_{2} + 2NaOH[/tex] is the double displacement reaction.
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