Question

A major component of gasoline is octane (C8H18). When octane is burned in air, it chemically reacts with oxygen gas (O2) to produce carbon dioxide (CO2) and water (H2O).
What mass of octane is consumed by the reaction of 2.3 g of oxygen gas?

Answer 1

At first chemical reaction should be written and balanced:

2C₈H₁₈ + 25O₂ = 16CO₂ + 18H₂O.

The molar masses of reactants should be found:

M(O₂)=2×16=32(g/mol),

M(C₈H₁₈)=8×12+18×1=114(g/mol).

Taking into account the reaction coefficients the mass of octane is found from a proportion:

x=2.3×2×114/25×32=0.6555(g).

Answer: 0.6555 g of octane.