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.
So to balance an equation, you need to get the same amount of each type of element on either side of the --> . So you pretty much are given the subscripts in the equations and you need to add coefficients (just normal numbers) in front of any formula that needs it, keeping anything balance.

turns into

These coefficient numbers are the molar ratios, so 2 moles of KCl3 for every 3 moles of O2 so 1. 3:2
Then you can use these ratios of find out how many moles of one thing are needed if you are given the amount of another.

and use cross multiplication to solve for whatever you don't know
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Explanation:
1. Elements are substances made of the same kind of atoms, unlike compounds that are combination for different kinds of atoms. The elements in the reaction therefore are;
Cl and O₃
2. Yes, the equation is balanced. There is the same number of each element on either side of the equation. One (1) CL and three (3) O atoms.
3. Ozone is reduced. Other the other hand, Cl is oxidized. Remember a reduction reaction may involve the loss of one or more oxygen atoms or the acceptance of electrons. This occurs for O₃ which is reduced to O₂.
4. The equation complies with the conservation of matter as in the first law of thermodynamics. The number of atoms for each element on the other side of the equation remains the same. This means no matter(which also translated to energy) has been created or destroyed in the process.
Noble gases already have eight electrons in their outer shells and they don't want to attract anymore. Since electronegativity measures the amount of attraction between an atom and an electron, noble gases do not have electronegativity.
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