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FeCl(3) is acidic towards litmus. On tre...

`FeCl_(3)` is acidic towards litmus. On treatment with excess of `NH_(4)SCN` it gives red coloured compound (A) and on treatment with excess of `K_(2)Cr_(2)O_(7)` in the presence of conc. `H_(2)SO_(4)`, it evolves deep red vapours of (B) on passing the vapours of (B) into `NaOH`, then adding a solution of acetic acid and lead acetate it gives yellow ppt. of compound of chromium (C)
The compound A is

A

`Fe(SCN)_(2)`

B

`Fe(SCN)_(3)`

C

`FeCl_(3)`

D

`NH_(4)[Fe(CN)_(4)]`

Text Solution

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The correct Answer is:
To solve the question step by step, we need to analyze the reactions involving `FeCl3`, `NH4SCN`, and `K2Cr2O7` in the presence of `H2SO4`. ### Step 1: Identify the reaction between `FeCl3` and `NH4SCN` When `FeCl3` (ferric chloride) is treated with excess `NH4SCN` (ammonium thiocyanate), a red-colored compound is formed. The reaction can be represented as follows: \[ \text{FeCl}_3 + 3 \text{NH}_4\text{SCN} \rightarrow \text{Fe(SCN)}_3 + 3 \text{NH}_4\text{Cl} \] The red-colored compound formed is known as ferric thiocyanate, which is denoted as `Fe(SCN)3`. ### Step 2: Identify the reaction between `FeCl3` and `K2Cr2O7` in the presence of `H2SO4` Next, when `FeCl3` is treated with excess `K2Cr2O7` (potassium dichromate) in the presence of concentrated `H2SO4`, deep red vapors are evolved. The reaction can be represented as follows: \[ \text{FeCl}_3 + \text{K}_2\text{Cr}_2\text{O}_7 + 4 \text{H}_2\text{SO}_4 \rightarrow \text{CrO}_2\text{Cl}_2 + \text{Fe}_2(\text{SO}_4)_3 + 2 \text{KHSO}_4 + 2 \text{HCl} \] The deep red vapors produced in this reaction are due to the formation of chromyl chloride, `CrO2Cl2`, which is denoted as compound B. ### Step 3: Passing vapors of B into `NaOH` When the vapors of `CrO2Cl2` (compound B) are passed into a solution of `NaOH`, a reaction occurs that produces sodium chromate: \[ \text{CrO}_2\text{Cl}_2 + 2 \text{NaOH} \rightarrow \text{Na}_2\text{CrO}_4 + 2 \text{NaCl} + \text{H}_2\text{O} \] ### Step 4: Reaction of sodium chromate with acetic acid and lead acetate Finally, when sodium chromate is treated with acetic acid and lead acetate, a yellow precipitate of lead chromate is formed, which is denoted as compound C: \[ \text{Na}_2\text{CrO}_4 + \text{Pb(CH}_3\text{COO)}_2 \rightarrow \text{PbCrO}_4 \downarrow + 2 \text{NaCH}_3\text{COO} \] The yellow precipitate formed is lead chromate, `PbCrO4`. ### Conclusion The compound A, which is formed when `FeCl3` is treated with `NH4SCN`, is ferric thiocyanate, represented by the formula `Fe(SCN)3`. ### Final Answer **The compound A is `Fe(SCN)3` (ferric thiocyanate).** ---
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FeCl_(3) is acidic towards litmus. On treatment with excess of NH_(4)SCN it gives red coloured compound (A) and on treatment with excess of K_(2)Cr_(2)O_(7) in the presence of conc. H_(2)SO_(4) , it evolves deep red vapours of (B) on passing the vapours of (B) into NaOH , then adding a solution of acetic acid and lead acetate it gives yellow ppt. of compound of chromium (C) What is the hybridisation of chromium in compound (C) ?

(i) An aqueous solution of a compound (A) is acidic towards litmus and (A) sublimes at about 300^(@)C . (ii) (A) on treatment with an excess of NH_(4)SCN gives a red coloured compound (B) and on treatment with a solution of K_(4)[Fe(CN)_(6)] gives a blue coloured compound (C). (iii) (A) on heating with excess of K_(2)Cr_(2)O_(7) in the presence of concentrated H_(2)SO_(4) evolves deep red vapours of (D). (iv) On passing the vapour of (D) into a solution of NaOH and then adding the solution of acetic acid and lead acetate, a yellow precipitate of compound (E) is obtained. Identify (A) to (E) and give chemical equations for the reactions.

(i) An aqueous solution of a compound (A) is acidic towards litmus and (A) sublimes at about 300^(@)C . (ii) (A) on treatment with an excess of NH_(4)SCN gives a red coloured compound (B) and on treatment with a solution of K_(4)[Fe(CN)_(6)] gives a blue coloured compound (C). (iii) (A) on heating with excess of K_(2)Cr_(2)O_(7) in the presence of concentrated H_(2)SO_(4) evolves deep red vapours of (D). (iv) On passing the vapour of (D) into a solution of NaOH and then adding the solution of acetic acid and lead acetate, a yellow precipitate of compound (E) is obtained. Identify (A) to (E) and give chemical equations for the reactions.

(i) An aqueous solution of a compound A is acidic towards litmus and A sublimes at about 300^(@)C (ii) A solution of A, on treatment with an excess of NH_(4)SCN , gives a red compound, and on treatment with a solution of K_(4)[Fe(CN)_(6)] , gives a blue compound. (iii) The solid A, on being heated with an excess of K_(2)Cr_(2)O_(7) in the presence of concentrated H_(2)SO_(4) , evolves deep red vapours of D. (iv) On passing the vapours of D into a solution of NaOH and then adding the solution of acetic acid and lead acetate, a yellow precipitate of a compound E is obtained. Q. Can compound A be prepared in the anhydrous form by strongly heating its hydrated crystals?

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