Question

Arrange the following in which they appear with decreasing temperature:
A. Tridymite,
B. Cristobalite,
C. Low quartz,
D. High quartz. Choose the correct answer from the options given below:

• A. A, D, C, B
• B. A, B, C, D
• C. B, A, D, C
• D. B, D, C, A

Hint:

Silica polymorphs in decreasing temperature are Cristobalite \(\rightarrow\) Tridymite \(\rightarrow\) High quartz \(\rightarrow\) Low quartz.

Answer 1

The Correct Option is C

Concept:
Silica \((SiO_2)\) has different polymorphs stable at different temperatures.

Step 1: Highest temperature form.
Cristobalite is stable at very high temperature among the given silica forms. \[ \text{Highest}=B \]

Step 2: Next temperature form.
Tridymite is stable below cristobalite but above quartz forms. \[ \text{Second}=A \]

Step 3: Quartz forms.
High quartz exists at higher temperature than low quartz. \[ D>C \]

Step 4: Final decreasing temperature order.
Thus, the sequence is: \[ \text{Cristobalite}>\text{Tridymite}>\text{High quartz}>\text{Low quartz} \] Using letters: \[ B>A>D>C \] \[ \therefore \text{Correct Answer is (C)} \]