When a little sulphur in a spoon is heated, it burns with a blue flame which slowly disappears after some time and we can feel a pungent odour. This pungent odour is due to

Options

A. carbon dioxide
B. sulphur dioxide
C. sulphur vapours
D. sulphuric acid.

Explanation

To determine the cause of the pungent odor when sulfur is heated, we can follow these steps:

### Step 1: Identify the substance being heated
When we heat sulfur, we start with elemental sulfur, which is represented as \( S_8 \) (a molecule consisting of eight sulfur atoms).

**Hint:** Remember that sulfur exists as a cyclic molecule in its elemental form.

### Step 2: Understand the reaction with oxygen
When sulfur is heated in the presence of oxygen, it undergoes combustion. The chemical reaction can be represented as:
\[ S_8 + O_2 \rightarrow SO_2 \]
This indicates that sulfur reacts with oxygen to form sulfur dioxide.

**Hint:** Combustion reactions typically involve a fuel (in this case, sulfur) reacting with oxygen.

### Step 3: Write the balanced chemical equation
To balance the reaction, we need to ensure that the number of atoms of each element is the same on both sides of the equation. The balanced equation for the combustion of sulfur can be written as:
\[ S_8 + 8 O_2 \rightarrow 8 SO_2 \]

**Hint:** Balancing chemical equations requires adjusting coefficients to ensure mass conservation.

### Step 4: Identify the product and its properties
The product of the combustion of sulfur is sulfur dioxide (\( SO_2 \)). This gas is known for its pungent odor, which is often described as sharp and irritating.

**Hint:** Think about the characteristics of gases produced in combustion reactions.

### Step 5: Conclude the cause of the odor
Since the pungent odor is associated with the gas produced during the combustion of sulfur, we can conclude that the odor is due to sulfur dioxide (\( SO_2 \)).

**Hint:** Consider the common odors associated with different chemical compounds, especially those formed from combustion.

### Final Answer
The pungent odor is due to sulfur dioxide (\( SO_2 \)).

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