A compound `(A)` is greenish crystalline salt, which gave the following reactions.
(i)Addition of `BaCl_(2)` solution to the solution of `(A)` results in the formation of white precipitate `(B)` which is insoluble in dilute `HCl`.
(ii)On heating `(A)`, water vapours and two oxides of sulphur `(C )` and `(D)` are liberated leaving a red brown residue `(E)`.
(iii)`(E)` dissolves in warm concentrated `HCl` to give a yellow solution `(F)`.
(iv)Solution `(F)` on treatment with thiocyanate ions gives blood red coloured compound `(G)`.
Identify the compounds from `(A)` to `(G)`.

Answer

To solve the problem step by step, we will identify the compounds from (A) to (G) based on the given reactions.

### Step 1: Identify Compound (A)
The question states that compound (A) is a greenish crystalline salt. The most common greenish crystalline salt is Iron(II) sulfate heptahydrate, which is represented as:
- **(A) = FeSO4·7H2O**

### Step 2: Reaction with BaCl2
The first reaction indicates that when (A) is treated with BaCl2, a white precipitate (B) is formed, which is insoluble in dilute HCl. The reaction can be written as:
- **FeSO4 + BaCl2 → BaSO4 (B) + FeCl2 + 7H2O**
Here, BaSO4 is the white precipitate that is insoluble in dilute HCl.
- **(B) = BaSO4**

### Step 3: Heating Compound (A)
The second reaction states that upon heating (A), water vapors and two oxides of sulfur (C and D) are released, leaving a red-brown residue (E). The decomposition of FeSO4 can be represented as:
- **2 FeSO4 → Fe2O3 (E) + SO2 (C) + SO3 (D) + H2O**
Thus, the red-brown residue is Iron(III) oxide.
- **(C) = SO2**
- **(D) = SO3**
- **(E) = Fe2O3**

### Step 4: Dissolving Residue (E) in HCl
The third reaction indicates that the red-brown residue (E) dissolves in warm concentrated HCl to give a yellow solution (F). The reaction can be represented as:
- **Fe2O3 + 6 HCl → 2 FeCl3 (F) + 3 H2O**
The yellow solution formed is Iron(III) chloride.
- **(F) = FeCl3**

### Step 5: Reaction with Thiocyanate Ions
The fourth reaction states that when solution (F) is treated with thiocyanate ions, a blood-red colored compound (G) is formed. The reaction can be represented as:
- **FeCl3 + 6 KSCN → K3[Fe(SCN)6] (G)**
This compound is known for its blood-red color.
- **(G) = K3[Fe(SCN)6]**

### Summary of Compounds
- **(A) = FeSO4·7H2O**
- **(B) = BaSO4**
- **(C) = SO2**
- **(D) = SO3**
- **(E) = Fe2O3**
- **(F) = FeCl3**
- **(G) = K3[Fe(SCN)6]**