Question

Consider the following reactions: \[ K_2Cr_2O_7 + 2 KOH \xrightarrow{ \text{heat} } [A] \] \[ [A] + H_2SO_4 \xrightarrow{} [B] + K_2SO_4 \] 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 \( CrO \)

Hint:

When potassium chromate reacts with sulfuric acid, it produces chromium trioxide. The reaction typically forms an orange solution due to the presence of \( K_2Cr_2O_7 \).

Answer 1

The Correct Option is C

This problem requires a step-by-step analysis of the provided chemical reactions to identify products [A] and [B]. The reactions are as follows:

1. Reaction 1:

\(K_2Cr_2O_7 + 2 KOH \xrightarrow{ \text{heat} } [A]\)

Potassium dichromate (\(K_2Cr_2O_7\)) reacts with potassium hydroxide (\(KOH\)) when heated. The resultant product, [A], is potassium chromate (\(K_2CrO_4\)). This transformation involves a change from the dichromate anion to the chromate anion.

1. Reaction 2:

\([A] + H_2SO_4 \xrightarrow{} [B] + K_2SO_4\)

In the second reaction, [A] (identified as \(K_2CrO_4\)) is reacted with sulfuric acid (\(H_2SO_4\)). This reaction regenerates the dichromate ion from the chromate ion. The products are potassium dichromate (\(K_2Cr_2O_7\)), which is [B], and potassium sulfate (\(K_2SO_4\)).

Consequently, the identified products for the reactions are:

• [A]: \(K_2CrO_4\)
• [B]: \(K_2Cr_2O_7\)

Based on these findings, the correctly matched products from the given options are:

\(K_2CrO_4\) and \(K_2Cr_2O_7\)