Question

When the substance A is added to a solution of $BaS{O_4}$, a yellow precipitate is formed.
A.What do you think substance A is likely to be?
B.Name the precipitate
C.Which type of reaction is this?

Answer 1

Hint: We know that there are two types of double displacement reaction. One kind of double displacement reaction is acid-base reaction and another kind of double displacement is precipitation reaction. We can say that an insoluble salt is formed when two solutions which have two soluble salts are combined. We can call this insoluble salt as precipitate

Complete answer:
We can say precipitation in chemical reactions refers to those reactions which happen in aqueous solution when two bonds which are ionic are joined to produce a salt that is insoluble known as precipitate.
We have to know that precipitation reaction could happen when two solutions which contain various salts are combined, and a pair of anion/cation in the left over solution results in insoluble salt, this salt comes out as precipitate out of solution.
A.When substance A is reacted with $BaS{O_4}$, we obtain a yellow precipitate. So, we can say that the substance A is potassium chromate.
A.When potassium chromate reacts with barium sulfate, the products formed are barium chromate and potassium sulfate. We can write the chemical reaction as,
${K_2}Cr{O_4} + BaS{O_4}\overset {} \leftrightarrows BaCr{O_4} + {K_2}S{O_4}$
The name of the yellow precipitate is barium chromate.
C.This reaction is a double displacement reaction as anions and cations of two compounds are interchanged to form new compounds.

Note:
We saw that double displacement reactions are of two types: acid-base reaction and precipitation reaction. In acid-base reaction, an acid and base gets reacted with one other to form salt and water. An example of this reaction is the reaction of hydrochloric acid and sodium hydroxide. We can call acid base reactions as neutralization reactions. Some of the applications of double displacement reactions are flame photometry, metals extraction, and indigestion of acids.