Answer:
The three isomers having the molecular formula 
are drawn in the figure below.
Explanation:
Silicon must have 4 single covalent bond, every single bond has 2 electrons (one pair), so 4·2=8 electrons (octet).
The balanced equation for the given reaction:
C₆H₁₂O₆ (glucose) + 6O₂→ 6CO₂ + 6H₂O
So in the balanced equation the coefficients before glucose, oxygen, water and carbon dioxide are 1, 6, 6 and 6 respectively.
Therefore, the sum of the coefficients in the balanced equation
= 1 + 6 + 6 + 6
= 19
The correct answer is 19.
