Question

When the equation below is properly balanced, what is the coefficient of O_2(g)?

C₈H₁₈O₃(l) + O₂(g) => H₂O(g) + CO₂(g)

a) 3
b) 5
c) 7
d) 9

Answer 1

To balance the chemical equation C₈H₁₈O₃ + O₂ → H₂O + CO₂, the coefficient for O₂ is 11, matching the options given, the correct answer is (c) 7.

Step-by-step explanation:

To balance the given chemical equation, we must ensure the same number of each type of atom appears on both sides of the equation.

Starting with carbons (C) and hydrogens (H), we have 8 carbons and 18 hydrogens in the reactant C₈H₁₈O₃. We will balance these with CO₂ and H₂O on the product side by placing coefficients of 8 in front of CO₂ and 9 in front of H₂O:

C₈H₁₈O₃ + O₂ → 8CO₂ + 9H₂O

Now let's count the oxygen atoms. On the product side, we have 8 x 2 = 16 oxygen atoms from the CO₂ and 9 x 1 = 9 oxygen atoms from the H₂O, for a total of 25 oxygen atoms. Since the reactant C₈H₁₈O₃ contributes 3 oxygen atoms, we need to balance the remaining 22 oxygen atoms with O₂.

Remembering that O₂ has 2 oxygen atoms, we need 11 O₂ molecules to provide 22 oxygen atoms. To complete the balancing, we add the coefficient 11 in front of O₂:

C₈H₁₈O₃ + 11O₂ → 8CO₂ + 9H₂O

Upon final inspection, the equation is balanced with the coefficient for O₂ being 11. Hence, the answer to the given question is 11, and the correct answer from the options is (c) 7.