Hydrogen gas is not obtained when zinc reacts with

Answer

**Step-by-Step Solution:**

1. **Understanding the Reactivity of Zinc**:
- Zinc is a metal that can react with various substances. However, its reactivity is not as high as some other metals like sodium or potassium.

2. **Identifying Possible Reactions**:
- When zinc reacts with acids (like hydrochloric acid), it typically produces hydrogen gas. For example, the reaction with hydrochloric acid can be represented as:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \]
- When zinc reacts with water, the reactivity of zinc plays a crucial role.

3. **Reactivity with Water**:
- Zinc does not react with cold water. This is because the reaction requires a more reactive metal or higher temperatures to produce hydrogen gas. The reaction with hot water or steam can produce hydrogen, but this is not the case with cold water.

4. **Conclusion**:
- Therefore, when zinc reacts with cold water, no hydrogen gas is produced. The answer to the question is that hydrogen gas is not obtained when zinc reacts with cold water.

**Final Answer**: Hydrogen gas is not obtained when zinc reacts with cold water.

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