JEE MainChemistryd and f Block Elements
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : In the industrial preparation of potassium dichromate, a hot concentrated solution of sodium dichromate is treated with potassium chloride. Reason (R) : Potassium dichromate is less soluble in water than sodium dichromate and crystallizes out on cooling. In the light of the above statements, choos
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
In the industrial preparation of potassium dichromate from chromite ore, sodium dichromate is first formed. Since sodium dichromate is highly soluble in water, it is converted to potassium dichromate by reacting its hot concentrated solution with potassium chloride. The reaction is: Na ₂ Cr ₂ O ₇ + 2 KCl K ₂ Cr ₂ O ₇ + 2 NaCl . The driving force for this reaction is the difference in solubility. Potassium dichromate is much less soluble in water than sodium dichromate. Therefore, upon cooling, K ₂ Cr ₂ O ₇ crystall