Alkanline earth metal nitrate `(A)` on heating decompose, leaving a solid residue `(B)` which goes into solution with dilute `HCI`. The solution of `(B)` gives a white precipitate `(C )` is dissolved in dilute `HCl` and the solution is treated with potassium chromae to get yellow precipitate `(D)`. The solution `(B)` with dilute `H_(2)SO_(4)` also gives a white precipitate `(E)` insoluble in diute `HCl` and nitric acid. the precipitate `(E)` is a part of a white pigment lithopone.
The solid residue `(B)` is

Options

A. `CaO`
B. `PbO`
C. `ZnO`
D. `BaO`

Explanation

To solve the problem step by step, we will analyze the information given about the alkaline earth metal nitrate and its decomposition products.

### Step 1: Identify the Alkaline Earth Metal Nitrate (A)
The question states that the alkaline earth metal nitrate (A) decomposes upon heating. The common alkaline earth metal nitrates are barium nitrate (Ba(NO3)2), calcium nitrate (Ca(NO3)2), magnesium nitrate (Mg(NO3)2), and strontium nitrate (Sr(NO3)2). Among these, barium nitrate is known to decompose to form a solid residue upon heating.

**Hint:** Look for the alkaline earth metal nitrate that is known to decompose upon heating.

### Step 2: Decomposition of Alkaline Earth Metal Nitrate
When barium nitrate (Ba(NO3)2) is heated, it decomposes to form barium oxide (BaO), nitrogen dioxide (NO2), and oxygen (O2). The balanced equation for this reaction is:
\[ 2 \text{Ba(NO}_3\text{)}_2 \rightarrow 2 \text{BaO} + 4 \text{NO}_2 + \text{O}_2 \]
Thus, the solid residue (B) formed after heating is barium oxide (BaO).

**Hint:** Consider the products formed during the thermal decomposition of the nitrate.

### Step 3: Reaction of Solid Residue (B) with Dilute HCl
The solid residue (B), which is barium oxide (BaO), reacts with dilute hydrochloric acid (HCl) to form barium chloride (BaCl2) and water (H2O):
\[ \text{BaO} + 2 \text{HCl} \rightarrow \text{BaCl}_2 + \text{H}_2\text{O} \]
This reaction indicates that the solution of (B) gives barium chloride in solution.

**Hint:** Identify the products formed when metal oxides react with acids.

### Step 4: Formation of White Precipitate (C)
The barium chloride (BaCl2) solution can then react with potassium chromate (K2CrO4) to form a yellow precipitate of barium chromate (BaCrO4):
\[ \text{BaCl}_2 + \text{K}_2\text{CrO}_4 \rightarrow \text{BaCrO}_4 \downarrow + 2 \text{KCl} \]
However, the question mentions a white precipitate (C). This could refer to the formation of barium sulfate (BaSO4) in a subsequent reaction.

**Hint:** Consider the possible precipitates formed when barium chloride reacts with other reagents.

### Step 5: Reaction of (B) with Dilute H2SO4
When barium oxide (BaO) reacts with dilute sulfuric acid (H2SO4), it forms barium sulfate (BaSO4), which is a white precipitate:
\[ \text{BaO} + \text{H}_2\text{SO}_4 \rightarrow \text{BaSO}_4 \downarrow + \text{H}_2\text{O} \]
This white precipitate (E) is insoluble in dilute HCl and nitric acid, confirming its identity as barium sulfate.

**Hint:** Look for the reactions that produce precipitates when metal oxides react with sulfuric acid.

### Step 6: Identify the Final Precipitate (E) and Its Relation to Lithopone
The precipitate (E), barium sulfate (BaSO4), is indeed a component of lithopone, which is a white pigment composed of zinc sulfide and barium sulfate.

**Conclusion:**
The solid residue (B) after the decomposition of alkaline earth metal nitrate (A) is barium oxide (BaO).

**Final Answer:**
The solid residue (B) is **BaO (barium oxide)**.