Black solid `underset(Delta)overset(KOH+Air)to underset(("green"))((A))overset(H_(2)SO_(4))to underset(("purple"))((B))+(C)`
(i) KI on reaction with alkali solution of (B) changes into a compound (D).
(ii) The colour of the compound (B) disappears on treatment with the acidic solution of `FeSO_(4)`
(iii) With cold conc. `H_(2)SO_(4)` compound (B) gives (E), which being explosive decomposes to yield (F) and oxygen. ltBrgt Q. Colour of the solution obtained, when ferrous sulphate reacts with acidic solution of (B):

Options

A. Colourless
B. Pink
C. Green
D. Yellow

Explanation

To solve the problem step by step, we will identify the compounds involved and their reactions based on the information provided.

### Step 1: Identify the Black Solid
The black solid mentioned in the question is likely manganese dioxide (MnO2). This is a common black solid that can undergo reactions with alkali and air.

**Hint:** Think about common black solids in inorganic chemistry and their reactions.

### Step 2: Reaction with KOH and Air
When MnO2 is heated in the presence of KOH and air, it forms potassium manganate (K2MnO4), which is green in color. Therefore, the green compound (A) is K2MnO4.

**Hint:** Consider the oxidation states of manganese and how they change during reactions with alkalis.

### Step 3: Reaction with H2SO4
Next, when K2MnO4 is treated with sulfuric acid (H2SO4), it produces potassium permanganate (KMnO4), which is purple in color. Thus, the purple compound (B) is KMnO4.

**Hint:** Recall the common reactions of manganates and permanganates with acids.

### Step 4: Reaction of KMnO4 with FeSO4
Now, we need to consider the reaction of KMnO4 (B) with ferrous sulfate (FeSO4) in an acidic medium. When KMnO4 reacts with FeSO4 in the presence of H2SO4, it leads to the formation of ferric sulfate (Fe2(SO4)3), manganese sulfate (MnSO4), potassium sulfate (K2SO4), and water.

**Hint:** Write out the balanced chemical equation to visualize the products formed.

### Step 5: Identify the Color of the Solution
The product Fe2(SO4)3 is a yellow-colored solution. Therefore, when ferrous sulfate reacts with an acidic solution of KMnO4, the resulting solution will be yellow.

**Hint:** Remember the colors associated with common iron salts and their oxidation states.

### Final Answer
The color of the solution obtained when ferrous sulfate reacts with the acidic solution of (B) (KMnO4) is **yellow**.

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