`FeCr_(2)O_(4)+NaOH+"air" to (A)+Fe_(2)O_(3)`
`(A)+(B) to Na_(2)Cr_(2)O_(7)`
`Na_(2)Cr_(2)O_(7)+X overset(Delta)to Cr_(2)O_(3)`
`Cr_(2)O_(3)+Y overset(Delta)to Cr`
`Na_(2)CrO_(4) and Fe_(2)O_(3)` are separated by :

Options

A. dissolving in conc. `H_(2)SO_(4)`
B. dissolving in `NH_(3)`
C. dissolving in `H_(2)O`
D. dissolving in dil. HCl

Answer

To solve the given problem step by step, we will analyze the reactions and identify the compounds involved.

### Step 1: Identify the Reaction of FeCr₂O₄ with NaOH and Air
The first reaction involves the compound FeCr₂O₄ reacting with sodium hydroxide (NaOH) and air (O₂). This reaction leads to the formation of sodium chromate (Na₂CrO₄) and iron(III) oxide (Fe₂O₃).

**Balanced Reaction:**
\[ \text{FeCr}_2\text{O}_4 + 8 \text{NaOH} + 4 \text{O}_2 \rightarrow 8 \text{Na}_2\text{CrO}_4 + 2 \text{Fe}_2\text{O}_3 + 4 \text{H}_2\text{O} \]

### Step 2: Identify the Reaction of (A) with (B)
Here, (A) is Na₂CrO₄ and (B) is sulfuric acid (H₂SO₄). When these two react, they yield sodium dichromate (Na₂Cr₂O₇).

**Reaction:**
\[ \text{Na}_2\text{CrO}_4 + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{Cr}_2\text{O}_7 + \text{Na}_2\text{SO}_4 + \text{H}_2\text{O} \]

### Step 3: Identify the Reaction of Na₂Cr₂O₇ with X
In this step, Na₂Cr₂O₇ reacts with a reducing agent (let's assume sulfur, S) to produce chromium(III) oxide (Cr₂O₃).

**Reaction:**
\[ \text{Na}_2\text{Cr}_2\text{O}_7 + 3 \text{S} \rightarrow \text{Cr}_2\text{O}_3 + 3 \text{Na}_2\text{SO}_4 \]

### Step 4: Identify the Reaction of Cr₂O₃ with Y
Now, Cr₂O₃ reacts with another reducing agent (let's assume aluminum, Al) to produce chromium metal (Cr).

**Reaction:**
\[ \text{Cr}_2\text{O}_3 + 6 \text{Al} \rightarrow 2 \text{Cr} + 3 \text{Al}_2\text{O}_3 \]

### Step 5: Separation of Na₂CrO₄ and Fe₂O₃
To separate Na₂CrO₄ and Fe₂O₃, we can utilize their solubility properties. Na₂CrO₄ is soluble in water, while Fe₂O₃ is insoluble. Therefore, they can be separated by dissolving in water.

**Final Answer:**
Na₂CrO₄ and Fe₂O₃ can be separated by dissolving in water.

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