In dry batteries the depolariser is

Options

A. `HgO`
B. `MnO_2`
C. `NH_4 Cl`
D. `ZnO`

Answer

To solve the question "In dry batteries the depolariser is", we can follow these steps:

### Step 1: Understand the Concept of a Depolarizer
A depolarizer is a substance used in primary cells (like dry batteries) to prevent the buildup of hydrogen gas bubbles during the discharge process. This is important because the accumulation of hydrogen gas can hinder the battery's performance.

**Hint:** Remember that a depolarizer helps to maintain the efficiency of the battery by preventing gas buildup.

### Step 2: Identify the Role of a Depolarizer
The depolarizer functions by accepting electrons during the discharge of the cell. This means that it acts as an oxidizing agent, which is essential for the chemical reactions taking place in the battery.

**Hint:** Think about how the depolarizer interacts with electrons during the battery's operation.

### Step 3: Analyze the Given Options
The options provided are:
- HDO
- MnO2
- Ammonium Chloride
- Zinc Oxide

We need to determine which of these substances is commonly used as a depolarizer in dry batteries.

**Hint:** Consider the common substances used in batteries and their functions.

### Step 4: Evaluate Each Option
- **HDO**: Not commonly recognized as a depolarizer in batteries.
- **MnO2 (Manganese Dioxide)**: Known to be used as a depolarizer in dry batteries.
- **Ammonium Chloride**: Typically used as an electrolyte, not a depolarizer.
- **Zinc Oxide**: Not used as a depolarizer in dry batteries.

**Hint:** Recall the specific functions of each substance in battery chemistry.

### Step 5: Conclusion
Based on the analysis, the correct answer is **MnO2 (Manganese Dioxide)**, as it is the substance used as a depolarizer in dry batteries.

**Final Answer:** The depolarizer in dry batteries is **MnO2 (Manganese Dioxide)**.