Given below are two statements:
Statement I: $\alpha$ and $\beta$ forms of sulphur can change reversibly between themselves with slow heating or slow cooling.
Statement II: At room temperature the stable crystalline form of sulphur is monoclinic sulphur.
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For sulfur allotropes, remember the key temperature: 369 K (96 °C). Below it, rhombic ($\alpha$) is stable. Above it, monoclinic ($\beta$) is stable. The transition between them is a classic example of enantiotropic allotropy.
To solve this question, let's analyze the given statements regarding the crystalline forms of sulphur.
Statement I: \(\alpha\) and \(\beta\) forms of sulphur can change reversibly between themselves with slow heating or slow cooling.
The \(\alpha\) form of sulphur is known as rhombic sulphur, while the \(\beta\) form is known as monoclinic sulphur.
Both these forms of sulphur can indeed transform into each other under different thermal conditions. Specifically, when rhombic sulphur (\(\alpha\)) is heated to temperatures above 96 °C, it transforms into monoclinic sulphur (\(\beta\)). Conversely, when monoclinic sulphur is cooled below 96 °C, it reverts to rhombic sulphur.
This reversible transformation upon heating or cooling is characteristic of these allotropes of sulphur.
Therefore, Statement I is true.
Statement II: At room temperature, the stable crystalline form of sulphur is monoclinic sulphur.
Monoclinic sulphur (\(\beta\)) is not stable at room temperature. Instead, the rhombic form (\(\alpha\)) is the stable crystalline form of sulphur at room temperature and below 96 °C.
As such, this statement is incorrect because it states that monoclinic sulphur is the stable form at room temperature, which is false.
As per the analysis above, the correct evaluation of the statements is that Statement I is true, but Statement II is false. Thus, the correct answer is: Statement I is true but Statement II is false.
