Sodium chromate, `Na_(2)CrO_(4)` is made commerically by :

Options

A. heating mixture of `Cr_(2)O_(3) and Na_(2)CO_(3)`
B. heating mixture of chromate ore and sodium carbonate in the presence of oxygen
C. heating sodium dichromate with sodium carbonate
D. reacting NaOH with chromic acid

Answer

To solve the question regarding the commercial production of sodium chromate (`Na2CrO4`), we will analyze the options provided and determine the correct method.

### Step-by-Step Solution:

1. **Understanding the Options**:
We are given four options for the commercial production of sodium chromate. They are:
- A) Heating a mixture of `Cr2O3` and `Na2CO3`
- B) Heating a mixture of chromate ore and sodium carbonate in the presence of oxygen
- C) Heating sodium dichromate with sodium carbonate
- D) Reacting `NaOH` with chromic acid

2. **Analyzing Each Option**:
- **Option A**: Heating `Cr2O3` (chromium(III) oxide) with `Na2CO3` (sodium carbonate) does not typically yield sodium chromate directly. This method is not commonly used for the commercial production of sodium chromate.

- **Option B**: Heating a mixture of chromate ore (which contains chromium) and sodium carbonate in the presence of oxygen is a known method for producing sodium chromate. This process involves the oxidation of chromium compounds in the ore to form sodium chromate.

- **Option C**: Heating sodium dichromate with sodium carbonate could yield sodium chromate, but this is not the primary commercial method used for production.

- **Option D**: Reacting `NaOH` (sodium hydroxide) with chromic acid does not lead to the commercial production of sodium chromate. This reaction is not efficient for large-scale production.

3. **Identifying the Correct Option**:
Based on the analysis, **Option B** is the most appropriate and commonly used method for the commercial production of sodium chromate. The reaction can be summarized as follows:
\[ \text{Chromate ore (FeCrO4) + Na2CO3 + O2} \rightarrow \text{Na2CrO4 + Fe2O3 + CO2} \]
This reaction indicates that heating chromate ore with sodium carbonate and oxygen produces sodium chromate along with iron(III) oxide and carbon dioxide.

### Conclusion:
The correct answer is **Option B**: Heating a mixture of chromate ore and sodium carbonate in the presence of oxygen.

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