When chromite ore `(FeCr_2O_4)` is heated with sodium carbonate in free access of air

Options

A. No gaseous product is formed
B. Iron (II) oxide is obtained
C. A water insoluble product which is dark brown in colour is formed
D. A water soluble product which is red in colour is obtained

Answer

To solve the question regarding the reaction of chromite ore `(FeCr_2O_4)` when heated with sodium carbonate in the presence of air, we can follow these steps:

### Step 1: Write the Reactants
The reactants in this reaction are chromite ore, which is `FeCr_2O_4`, and sodium carbonate, which is `Na_2CO_3`.

### Step 2: Identify the Reaction Conditions
The reaction occurs in the presence of air (which provides oxygen). This is important as it will influence the oxidation states of the products formed.

### Step 3: Write the Balanced Chemical Equation
When chromite ore is heated with sodium carbonate in the presence of air, the following reaction occurs:

\[ 4 FeCr_2O_4 + 8 Na_2CO_3 + 7 O_2 \rightarrow 2 Fe_2O_3 + 8 Na_2CrO_4 + 8 CO_2 \]

### Step 4: Identify the Products
From the balanced equation, we can see that the products formed are:
- Iron(III) oxide, `Fe_2O_3`, which is a dark brown or red-brown color.
- Sodium chromate, `Na_2CrO_4`, which is a water-soluble product.
- Carbon dioxide, `CO_2`, which is a gas.

### Step 5: Analyze the Options
Given the options:
1. No gaseous products are formed. (Incorrect)
2. Iron(II) oxide is obtained. (Incorrect)
3. A water-insoluble product which is dark brown in color is formed. (Correct - referring to `Fe_2O_3`)
4. A water-soluble product which is red in color is obtained. (Partially correct - refers to `Na_2CrO_4`, but not the main focus)

### Conclusion
The correct answer is option 3: A water-insoluble product which is dark brown in color is formed.

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