Question

Why is the reaction between sodium sulphate and barium chloride called chrmical double displacement?

Answer 1

Because here barium displaces sodium from sodium sulphate and itself forms barium sulphate. On the other hand, sodium displaces barium from barium chloride and itself forms sodium sulphate. According to the defination of double displacement reaction that a rectant that reacts with another reactant and undergoes mutual exchange of ions, this reaction stands true. Hence it is a double displacement reaction.
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Answer 2

 REACTION ;   ''Na2SO4  +  BaCl2 ----------> NaCl +BaSO4

This is a DOUBLE DISPLACEMENT REACTION ''

REASON ; Because in this reaction their is mutual displacement of ions.
Dislaplacement takes place twice''.