Question

When potassium chromate is added to the solution of barium sulphate, a precipitate of barium chromate is formed. What is the colour of it?
a.) Blue
b.) Red
c.) Yellow
d.) Green

Answer 1

Hint: Potassium chromate used as a reactant in this reaction is in powdered form. It is yellow in colour. The other reactant, barium sulphate is white in colour. Write down the chemical reaction, balance it, and the product is formed as a precipitate, and it’s colour can be identified.

Complete step by step answer:
Firstly, potassium chromate taken to perform the reaction is of white colour in the powdered form whereas, barium sulphate has white colour.
Before the addition of barium sulphate into the potassium chromate, it is dissolved in water leading to the milky-white colour.
Now, when we will add the milky-white solution to the potassium chromate, a new product is formed known as barium chromate which is yellow in colour.
Now, we will write the chemical reaction formed by the reaction of potassium chromate with the solution of barium sulphate is
K$_2$CrO$_4$ + BaSO$_4$ $\rightarrow$ K$_2$SO$_4$ + BaCrO$_4$
In this reaction, K$_2$CrO$_4$ is potassium chromate, BaSO$_4$ is barium sulphate, K$_2$SO$_4$ is potassium sulphate, and BaCrO$_4$ is barium chromate.
This reaction takes place by double-displacement.
Thus, the barium chromate formed is yellow in colour. The correct option is C.

Note: Don’t get confused between the solutions taken to perform the reaction. Carefully examine their colours while performing, as the colour of the reactants will help in identifying the colour of the end product.