Select the incorrect statement.

Options

A. Spinach, lemon and curd are the natural sources of oxalic acid, citric acid and lactic acid respectively.
B. The atmosphere of Mars is made up of thick white and yellowish clouds of sulphuric acid.
C. Slaked lime is used for white washing.
D. During electrolysis of brine, `Cl_(2)` gas is given off at the anode and `H_(2)` gas at the cathode.

Explanation

To solve the question of selecting the incorrect statement, we will analyze each statement provided in the context of acids, bases, and salts.

### Step-by-Step Solution:

1. **Understanding the Statements**:
- The question asks us to identify which statement is incorrect among the given options.

2. **Analyzing Statement 1**:
- **Statement**: "Spinach, lemon, curd are the natural sources of oxalic, acetic acid and lactic acid respectively."
- **Analysis**:
- Spinach is indeed a natural source of oxalic acid.
- Lemon is a natural source of citric acid, not acetic acid.
- Curd is a natural source of lactic acid.
- **Conclusion**: This statement contains an error regarding lemon, making it partially incorrect.

3. **Analyzing Statement 2**:
- **Statement**: "The atmosphere of Mars is made up of thick white and yellowish clouds of sulphuric acid."
- **Analysis**:
- The atmosphere of Venus, not Mars, is known for having thick clouds of sulphuric acid.
- **Conclusion**: This statement is incorrect.

4. **Analyzing Statement 3**:
- **Statement**: "The slate line is used for white washing."
- **Analysis**:
- The term "slate line" seems to be a confusion; however, if it refers to slaked lime (calcium hydroxide), then it is indeed used for whitewashing.
- **Conclusion**: This statement is correct.

5. **Analyzing Statement 4**:
- **Statement**: "During electrolysis of brine, Cl2 gas is given off at anode and H2 gas at cathode."
- **Analysis**:
- During the electrolysis of brine (saltwater), chlorine gas (Cl2) is produced at the anode, and hydrogen gas (H2) is produced at the cathode.
- **Conclusion**: This statement is correct.

6. **Final Decision**:
- The incorrect statement among the options is the second one: "The atmosphere of Mars is made up of thick white and yellowish clouds of sulphuric acid."

### Answer:
The incorrect statement is: **"The atmosphere of Mars is made up of thick white and yellowish clouds of sulphuric acid."**

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