Question

The color change is due to the change in oxidation state of potassium chromate
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but reason is incorrect.
D. Assertion is incorrect but Reason is correct

Answer 1

The potassium chromate is basic in nature therefore it gives a yellow color solution on reacting with acid it forms a acidic salt known as potassium dichromate which is a dipotassium salt of dichromic acid.

Complete step by step answer:
The potassium chromate is a chemical compound with chemical formula ${K_2}Cr{O_4}$. In potassium chromate two potassium cations are present and one chromate ion is present.
The solution of potassium chromate is yellow in color. On reacting with acid, the potassium chromate changes its color as a new product is formed.
The reaction of potassium chromate with sulphuric acid is shown below.
$2{K_2}Cr{O_4} + {H_2}S{O_4} \to {K_2}C{r_2}{O_7} + {K_2}S{O_4} + {H_2}O$
In this reaction two moles potassium chromate reacts with one mole of sulphuric acid to form one mole of potassium dichromate, one mole of potassium sulphate and water.
The potassium chromate is slightly basic in nature, reacting with acid it changes its color from yellow to red.
The oxidation of chromium in potassium chromate is +6 and after reacting with sulphuric acid it forms potassium dichromate. The oxidation state of potassium dichromate is +6.
The oxidation state does not change during the reaction.
Thus, Assertion is correct but reason is not correct for the assertion.
So, the correct answer is “Option C”.

Note:
Potassium dichromate is used as an oxidizing agent. Potassium dichromate on reacting with base potassium hydroxide forms potassium chromate and water.