Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Phosphorous oxide is a glass former.
Reason R: Phosphorus oxide is considered a substitute for silica.
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both A and R are correct and R is the correct explanation of A.
• B. Both A and R are correct but R is NOT the correct explanation of A.
• C. A is correct but R is not correct.
• D. A is not correct but R is correct.

Hint:

Logic Tip: Phosphorus Oxide ($P_2O_5$) is one of the "Big Three" glass formers (along with Silica and Boron).

Answer 1

The Correct Option is B

Concept:
In ceramic chemistry, materials are classified by their atomic roles. Glass formers (network formers) are the structural backbone of any glaze.

Step 1:
The three primary glass-forming oxides in ceramics are Silica ($SiO_2$), Boric Oxide ($B_2O_3$), and Phosphorous Oxide ($P_2O_5$). These molecules can form complex, random, 3D structural networks when cooled from a liquid state.

Step 2:
Because Phosphorous oxide ($P_2O_5$) is structurally capable of creating a glass network on its own, it is officially classified as a glass former. Thus, Assertion A is correct.

Step 3:
Because it is a glass former, $P_2O_5$ (often introduced via bone ash) can be used to substitute for or supplement silica in highly specialized ceramic bodies (like bone china) and specialty optical glasses. Thus, Reason R is correct.

Step 4:
Does being a substitute (R) explain why it is a glass former (A)? No, the logic flows the other way. It can be used as a substitute because its fundamental chemical nature is a glass former. Therefore, R is a factual consequence, not the explanatory cause of A.

Step 5:
Both statements are factually true in ceramic chemistry, but R does not correctly explain A. Option 2 is correct. \[ \boxed{\text{(2) Both A and R are correct but R is NOT the correct explanation of A.}} \]