Question

Liquid octane reacts with gaseous oxygen gas to produce gaseous carbon dioxide and gaseous water . What is the theoretical yield of carbon dioxide formed from the reaction of of octane and of oxygen gas? Be sure your answer has the correct number of significant digits in it.

Liquid octane reacts with gaseous oxygen gas (02) to produce gaseous carbon dioxide (CO2) and gaseous water (H2O). What is the theoretical yield of carbon dioxide formed from the reaction of 36.6 g of octane and 202. g of oxygen gas? Be sure your answer has the correct number of significant digits in it. x 6 ?

Answer 1

Molar mass of C₈H₁₈ = (8 $\times$ 12.01 ) + ( 18 $\times$ 1.0079 ) = 114.22 g / mol

Molar mass of O ₂ = ( 2 $\times$ 16.00 ) = 32.00 g / mol

Molar mass of CO ₂ = 12.01 + ( 2 $\times$ 16.00 ) = 44.01 g /mol

Firstly, we will find limiting reactant.

Consider a given reaction, 2 C₈H₁₈ (l) + 25 O ₂ (g) 16 CO ₂ (g) +18 H₂O (g)

From reaction,2 mol C₈H₁₈ $\equiv$ 25 mol O ₂

$\therefore$ 2 $\times$ 114.22 g C₈H₁₈$\equiv$ 25 $\times$ 32.00 g O ₂

$\therefore$ 36.6 g C₈H₁₈ $\equiv$ (25 $\times$ 32.00 $\times$ 36.6 / 2 $\times$ 114.22 ) g O ₂

36.6 g  C₈H₁₈  $\equiv$ 128.17 g O ₂

For complete reaction of 36.6 g octane , 128.17 g oxygen is required. Provided amount of oxygen is 202 g. Hence, oxygen is excess reactant and octane is limiting reactant . Yield of carbon dioxide will depend on amount of octane.

From reaction,2 mol C₈H₁₈ $\equiv$ 16 mol CO ₂

$\therefore$ 2 $\times$ 114.22 g C₈H₁₈ $\equiv$ 16 $\times$ 44.01 g CO ₂

$\therefore$ 36.6 g C₈H₁₈ $\equiv$ (16 $\times$ 44.01 $\times$ 36.6 / 2 $\times$ 114.22 ) g CO ₂

36.6 g C₈H₁₈ $\equiv$ 112.8 g CO ₂

Answer : Theoretical yield of carbon dioxide = 113 g