Understanding the Freezing Point of Sulphur Dioxide

The question asks for the approximate freezing point of sulphur dioxide ($\text{SO}_2$). The freezing point is the temperature at which a substance changes from a liquid state to a solid state under standard atmospheric pressure. This is an important physical property used to identify substances and understand their behavior at different temperatures.

Based on chemical data, the freezing point of sulphur dioxide is approximately $-75.2^\circ\text{C}$. This means that at temperatures below $-75.2^\circ\text{C}$, sulphur dioxide will exist as a solid, while above this temperature it will be a liquid (up to its boiling point).

Let's look at the given options and compare them:

• $-87.7^\circ\text{C}$: This value is significantly lower than the known freezing point of $\text{SO}_2$.
• $-56.6^\circ\text{C}$: This value is the melting/freezing point of benzene.
• $-75.2^\circ\text{C}$: This value aligns with the known freezing point of sulphur dioxide.
• $-135.8^\circ\text{C}$: This value is much lower and corresponds to the freezing point of carbon disulfide ($\text{CS}_2$).

Therefore, the approximate freezing point of sulphur dioxide is $-75.2^\circ\text{C}$.

Revision Table: Sulphur Dioxide Properties

Additional Information on Sulphur Dioxide ($\text{SO}_2$)

Sulphur dioxide is a chemical compound with the formula $\text{SO}_2$. It is a toxic gas with a pungent, irritating odor. It is produced naturally by volcanic activity and industrially by the combustion of fossil fuels containing sulfur compounds. $\text{SO}_2$ is a significant air pollutant and a primary precursor to acid rain when it reacts with water vapor in the atmosphere to form sulfuric acid.

Key characteristics of sulphur dioxide:

• It is a colorless gas at room temperature.
• It is denser than air.
• It is soluble in water.
• It is a major component in the production of sulfuric acid ($\text{H}_2\text{SO}_4$).
• It can be used as a disinfectant, a refrigerant (though less common now), and a food preservative (e.g., in dried fruits and wines).

Understanding its physical properties, like the freezing point, boiling point, and density, is crucial for safe handling, storage, and transportation of sulphur dioxide.