Electrolysis is used to obtain chlorine and caustic soda from_________.

Options

A. HCl
B. Common salt
C. `MgCl_2`
D. `CaCl_2`

Answer

To answer the question about what electrolysis is used to obtain chlorine and caustic soda from, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Electrolysis**: Electrolysis is a chemical process that uses electricity to drive a non-spontaneous reaction. It is commonly used to decompose compounds into their elements or simpler compounds.

2. **Identify the Compounds**: In this case, we are looking for the source material from which chlorine and caustic soda (sodium hydroxide, NaOH) can be produced through electrolysis.

3. **Recognize the Common Source**: The electrolysis of brine (a concentrated solution of sodium chloride, NaCl) is a well-known method to produce chlorine gas and sodium hydroxide.

4. **Write the Reaction**: During the electrolysis of brine, the following reactions occur:
- At the anode (positive electrode), chloride ions (Cl-) are oxidized to produce chlorine gas (Cl2).
- At the cathode (negative electrode), water is reduced to produce hydroxide ions (OH-) and hydrogen gas (H2). The hydroxide ions combine with sodium ions (Na+) from the brine to form sodium hydroxide (NaOH).

5. **Conclusion**: Therefore, the answer to the question is that electrolysis is used to obtain chlorine and caustic soda from **brine**.

### Final Answer:
Electrolysis is used to obtain chlorine and caustic soda from **brine**.

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