Dilute hydrochloric acid is added to granulated Zinc taken in a test tube the following observation
I.The surface of metal becomes shining
II.The reaction mixture turns milky
III.Odour of a pungent smelling gas is recorded
IV.A colourless and odourless gas is evolved
Choose the correct option

Options

A. only I
B. only II
C. Only III
D. ONLY IV

Answer

To solve the question regarding the observations made when dilute hydrochloric acid is added to granulated zinc, we can analyze each observation step by step.

### Step-by-Step Solution:

1. **Identify the Reaction**:
- When zinc (Zn) reacts with dilute hydrochloric acid (HCl), a chemical reaction occurs. Zinc displaces hydrogen from the acid, leading to the formation of zinc chloride (ZnCl₂) and hydrogen gas (H₂).
- The balanced chemical equation for this reaction is:
\[ \text{Zn (s)} + 2 \text{HCl (aq)} \rightarrow \text{ZnCl}_2 \text{(aq)} + \text{H}_2 \text{(g)} \]

2. **Analyze Observation I**:
- *The surface of the metal becomes shining*:
- This observation is likely due to the reaction removing any oxide layer from the zinc, making it appear shiny. However, this is not a definitive observation of the reaction itself.

3. **Analyze Observation II**:
- *The reaction mixture turns milky*:
- This observation is incorrect. The products of the reaction (zinc chloride and hydrogen gas) do not produce a milky solution. A milky appearance is usually associated with the formation of insoluble salts or precipitates, which does not occur here.

4. **Analyze Observation III**:
- *Odour of a pungent smelling gas is recorded*:
- This observation is also incorrect. Hydrogen gas (H₂) produced in the reaction is colorless and odorless. There is no pungent smell associated with this gas.

5. **Analyze Observation IV**:
- *A colourless and odourless gas is evolved*:
- This observation is correct. The gas evolved during the reaction is hydrogen (H₂), which is indeed colorless and odorless.

### Conclusion:
Based on the analysis of the observations:
- The correct observation is **IV**: A colourless and odourless gas is evolved.

### Final Answer:
The correct option is **IV**.

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