Question

Balanced Equation:
2C8H18 + 25O2 --> 16CO2 + 18H20
1, If 4 moles of octane, C8H18, were burned how many moles of oxygen were also used?
a. 30 moles
b. 38 moles
c 50 moles
d 25 moles
2. If you had 50 moles of each reactant present in a flask, which one would be the limiting reactant?
a. C4H10
b. CO2
c. O2
d. H20

e. None, they would tie

Answer 1

The balanced reaction is as follows:

2C₈H₁₈ + 25O₂ 16CO₂ + 18H₂O

1)

Moles of octane(C₈H₁₈) = 4 mol

Use the moles of octane and the mole ratio from the balanced reaction and determine the moles of oxygen as follows:

= 4 mol C₈H₁₈ x (25 mol O₂/ 2 mol C₈H₁₈)

= 50 mol O₂

Thus, the moles of O₂ is 50 mol.

Thus, option(c) 50 moles is the correct answer.

2)

The balanced reaction is as follows:

2C₈H₁₈ + 25O₂ 16CO₂ + 18H₂O

Moles of octane(C₈H₁₈) = 50 mol

Moles of oxygen(O₂) = 50 mol

Determine the number of moles of C₈H₁₈ required to react completely with 50 mol O₂ as follows:

= 50 mol O₂ x ( 2 mol C₈H₁₈/ 25 mol O₂)

= 4 mol C₈H₁₈

Similarly, Determine the number of moles of O₂ required to react completely with 50 mol C₈H₁₈ as follows:

= 50 mol C₈H₁₈ x ( 25 mol O₂/ 2 mol C₈H₁₈)

= 625 mol O₂

Thus, the number of moles of O₂ required to react completely with 50 mol C₈H₁₈, is more than the given moles of O₂.

Thus, oxygen is the limiting reactant.

Thus, option (c) O₂ is the limiting reactant.