Question

Which type of chemical reaction is represented by the reaction –
$BaC{l_2} + N{a_2}S{O_4} \to BaS{O_4} + 2NaCl$
A.Displacement
B.Combination
C.Decomposition
D.Double Displacement

Answer 1

This reaction involves the exchange of sulphate ion and chlorine ion between two compounds. The reaction which involves the exchange of two ions between two compounds is called double displacement reaction.

Complete step by step answer:
Displacement reaction: The reaction in which the atom displaces another atom in a molecule is called displacement reaction. We can also call it a single displacement reaction. It is a kind of oxidation – reduction chemical reaction. For example, when chlorine reacts with sodium bromide, the chlorine takes the place of bromine because reactivity of chlorine is greater than bromine.
$C{l_2} + 2NaBr \to 2NaCl + B{r_2}$
Combination reaction: Combination reaction can be defined as the reaction in which two or more elements or compounds combine and form a single compound as a product. When this reaction takes place between metals and non – metals the product we get is ionic solid. For example, the reaction between carbon and oxygen gives carbon dioxide as a product.
$C + {O_2} \to C{O_2}$
In this reaction, when bonds are formed between the reactants, then, the heat is released, so combination reactions are exothermic.

Decomposition reaction: This reaction can be defined as the reaction in which the reactant is broken down into two or more products. Decomposition reaction is the opposite of combination reaction but the decomposition reaction can be both endothermic and exothermic. The example for this reaction is –
$NaCl \to Na + Cl$
Double Displacement reaction: The reaction in which the reaction involves the exchange of two ions between two compounds to form two new compounds. The example for this reaction is –
$F{e_2}{O_3} + 6HCl \to 2FeC{l_3} + 3{H_2}O$

According to the question, the reaction is –
$BaC{l_2} + N{a_2}S{O_4} \to BaS{O_4} + 2NaCl$
In the above reaction, there is an exchange of $S{O_4}$ and $C{l_2}$ ions between barium and sodium compounds and form new compounds which are barium sulphate and sodium chloride. Therefore, this is the double displacement reaction.
Hence, option (D) is the correct answer.

Note: In the aqueous solutions, the ions precipitate and the ions are exchanged therefore, the double displacement reaction mostly takes place in the aqueous solutions.