Question

What is the stoichiometric coefficient for oxygen gas when the following equation is balanced using the lowest, whole-number coefficients?

________ C₅H₁₂(g) + ________ O₂(g) → ________ CO₂(g) + ________ H₂O(l)

a)6 b)3 c)8 d)10

Answer 1

Ans = c) 8.

C₅H₁₂(g) + 8O₂(g)    5CO₂(g) + 6H₂O(l)

Carbon Hydrogen Oxygen

Reactant 5 12 2   

Product 1 2 3

For balancing C in product side, we can multiply by 5. To Hydrogen by 6 & we get.

Carbon Hydrogen Oxygen

Reactant 5 12 2   

Product 1 x 5 2 x 6 3

Balanced 5 12

5 CO₂ 6H₂O

Now total oxygen on product side becomes 16. ( 10 from CO2 & 6 from H2O)

Therefore coefficient 8 is aded to O2 on reactant side so as to oxygen becomes 16 & get balanced.