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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Saurabh 1
It's all about the valency difference between the Si and Al . You might be aware of the fact that Valency of Si is 4+ Valency of Al is 3+ As per question 2 silicate atoms are present in tha augite per 12 oxygen atoms. So total valency= 2×4 = 8 (Valency of Si is 4) While as per given question, only Al replaces Si atoms. So Si will definitely be replaced by 2 Al atoms which contributed towards the valency of 2×3=6 (valency of Al is 3) . Remaining sites will be acquired by Al, so number of tetrahedral Al is 2. Note: This one seems to be quite irrelevant. Do check the question again and let me know in case of any correction or confusion.