Consider the following reactions: K2Cr2O7 + 2 KOH heat [A] [A] + H2SO4 [B] + K2SO4 The products [A] and [B], respectively are:

Consider the following reactions: K2Cr2O7 + 2 KOH heat [A] [A] +… — Solution | JEE Chemistry

MCQEasyJEE 2025Potassium Dichromate & Permanganate

Consider the following reactions: $K_2Cr_2O_7 + 2 KOH \xrightarrow{ heat } [A]$ $[A] + H_2SO_4 \xrightarrow{} [B] + K_2SO_4$ The products [A] and [B], respectively are:

A
$K_2Cr(OH)_6$ and $Cr_2O_3$
B
$K_2CrO_4$ and $Cr_2O_3$
C
$K_2CrO_4$ and $K_2Cr_2O_7$
D
$K_2CrO_4$ and $CrO$

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given:

$K_2Cr_2O_7 + 2KOH \xrightarrow{\text{heat}} [A]$
$[A] + H_2SO_4 \rightarrow [B] + K_2SO_4$

Find: The products [A] and [B].

Potassium dichromate in alkaline medium converts to potassium chromate. Hence,

K_2Cr_2O_7 + 2KOH \xrightarrow{\text{heat}} 2K_2CrO_4 + H_2O

So, [A] = $K_2CrO_4$ .

Now acidification of chromate converts it back to dichromate. Therefore,

2K_2CrO_4 + H_2SO_4 \rightarrow K_2Cr_2O_7 + K_2SO_4 + H_2O

So, [B] = $K_2Cr_2O_7$ .

Therefore, the products are $K_2CrO_4$ and $K_2Cr_2O_7$ . The correct option is C.

Common mistakes

Confusing chromate with dichromate in basic medium. In alkaline solution, dichromate converts to chromate, not the other way around. Check whether the medium is basic or acidic before deciding the product.
Assuming sulfuric acid reduces chromium to $Cr_2O_3$ . Here sulfuric acid only acidifies the chromate solution, converting chromate to dichromate. Do not infer a redox product when the reaction is an acid-base chromate-dichromate equilibrium.

Practice more Potassium Dichromate & Permanganate questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Start free trial More on Potassium Dichromate & Permanganate

Answer

Step-by-step solution

Common mistakes

Practice more Potassium Dichromate & Permanganate questions

Related questions