When washing soda is treated with hydrochloric acid, it gives off a colourless gas with a lot of effervescence. Identify the gas.

Options

A. `CO_(2)`
B. `O_(2)`
C. CO
D. `Cl_(2)`

Explanation

To identify the gas evolved when washing soda is treated with hydrochloric acid, we can follow these steps:

### Step 1: Identify the Reactants
- Washing soda is chemically known as sodium carbonate (Na2CO3).
- Hydrochloric acid is represented by the formula HCl.

### Step 2: Write the Chemical Reaction
- When sodium carbonate reacts with hydrochloric acid, the reaction can be written as:
\[ \text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{O} + \text{CO}_2 \]
- This equation shows that sodium carbonate reacts with hydrochloric acid to produce sodium chloride (NaCl), water (H2O), and carbon dioxide (CO2).

### Step 3: Identify the Evolved Gas
- From the balanced chemical equation, we can see that the gas produced is carbon dioxide (CO2).
- Carbon dioxide is a colorless gas that is known to produce effervescence (bubbles) when it is released.

### Step 4: Confirm the Gas
- To confirm that the gas evolved is indeed carbon dioxide, you can perform a simple test:
- Pass the gas through lime water (which is a solution of calcium hydroxide, Ca(OH)2).
- If carbon dioxide is present, it will react with lime water to form calcium carbonate (CaCO3), which is insoluble in water and will make the lime water turn milky:
\[ \text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O} \]

### Conclusion
- The colorless gas that is evolved with a lot of effervescence when washing soda is treated with hydrochloric acid is carbon dioxide (CO2).

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