Question

How many moles of oxygen gas are required to combust 2.8 mol octane, c8h18, completely to co2 and h2o?

Answer 1

The moles of oxygen gas required to combust 2.8 mol octane is $\boxed{{\text{35 moles}}}$

Further explanation:

The chemical reaction that contains equal number of atoms of the different elements in the reactant as well as in the product side is known as balanced chemical reaction. The chemical equation is required to be balanced to follow the Law of the conservation of mass.

Combustion reaction is the reaction in which the reactant reacts with molecular oxygen to form carbon dioxide and water molecule. Molecular oxygen acts as the oxidizing agent in these reactions. The large amount of heat is released and therefore combustion reactions are exothermic reaction.

The steps to balance a chemical reaction are as follows:

Step1: Complete the reaction and write the unbalanced symbol equation.

In the combustion reaction, ${{\text{C}}_8}{{\text{H}}_{18}}$ reacts with ${{\text{O}}_2}$ to form ${\text{C}}{{\text{O}}_{\text{2}}}$ and ${{\text{H}}_{\text{2}}}{\text{O}}$. The physical state of ${{\text{C}}_8}{{\text{H}}_{18}}$ is gas, ${{\text{O}}_2}$ is gas, ${\text{C}}{{\text{O}}_{\text{2}}}$ is gas and ${{\text{H}}_{\text{2}}}{\text{O}}$ is gas. The unbalanced chemical equation is as follows:

${{\text{C}}_8}{{\text{H}}_{18}}\left(g\right)+{{\text{O}}_2}\left(g\right)\to{\text{C}}{{\text{O}}_{\text{2}}}\left(g\right)+{{\text{H}}_{\text{2}}}{\text{O}}\left(g\right)$

Step2: Then we write the number of atoms of all the different elements that are present in a chemical reaction in the reactant side and product side separately.

• On reactant side,

Number of carbon atoms is 8.

Number of hydrogen atoms is 18.

Number of oxygen atoms is 2.

• On product side,

Number of carbon atoms is 1.

Number of hydrogen atoms is 2.

Number of oxygen atoms is 3.

Step3: Initially, we try to balance the number of other atoms of elements except for carbon, oxygen, and hydrogen by multiplying with some number on any side but in the combustion reaction there is only carbon, hydrogen, and oxygen atom.

Step 4: After this, we balance the number of atoms of carbon and then hydrogen atom followed by oxygen atoms.

To balance the number of atoms we have to multiply ${{\text{O}}_2}$ by $\frac{{25}}{2}$, ${\text{C}}{{\text{O}}_{\text{2}}}$ by 8 and ${{\text{H}}_{\text{2}}}{\text{O}}$ by 9.

This gives,

${{\text{C}}_8}{{\text{H}}_{18}}\left(g\right)+\boxed{\frac{{25}}{2}}{{\text{O}}_2}\left(g\right)\to\boxed8{\text{C}}{{\text{O}}_{\text{2}}}\left(g\right)+\boxed9{{\text{H}}_{\text{2}}}{\text{O}}\left(g\right)$

Step 5: Since the balanced reaction must contain coefficients as a whole number. To make all the coefficients whole number we have to multiply whole equation by 2. This gives the balanced chemical equation as follows:

${\text{2}}{{\text{C}}_8}{{\text{H}}_{18}}\left(g\right)+25{{\text{O}}_2}\left(g\right)\to8{\text{C}}{{\text{O}}_{\text{2}}}\left(g\right)+9{{\text{H}}_{\text{2}}}{\text{O}}\left(g\right)$

According to the stoichiometry, 2 moles of ${{\mathbf{C}}_{\mathbf{8}}}{{\mathbf{H}}_{{\mathbf{18}}}}$ react with 25 moles of ${{\mathbf{O}}_{\mathbf{2}}}$ to give 8 moles of ${\mathbf{C}}{{\mathbf{O}}_{\mathbf{2}}}$ and 9 moles of ${{\mathbf{O}}_{\mathbf{2}}}$.

So the number of moles of ${{\mathbf{O}}_{\mathbf{2}}}$ formed by 2.8 moles of ${{\mathbf{C}}_{\mathbf{8}}}{{\mathbf{H}}_{{\mathbf{18}}}}$ is calculated as follows:

$\begin{gathered}{\text{Moles of }}{{\text{O}}_2}{\mathbf{=}}\left({\frac{{25\;{\text{mol}}}}{{2\;{\text{mol}}}}}\right)\times\left({2.8\;{\text{mol}}}\right)\\=35\;{\text{mol}}\\\end{gathered}$

Hence, the moles of ${{\mathbf{O}}_{\mathbf{2}}}$ produced is 35 moles.

Learn more:

1. Balanced chemical equation: brainly.com/question/1832039

2. Balanced equation for the given chemical reaction: brainly.com/question/2612756

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Chemical reaction and equation

Keywords: Balancing, C8H18, O2, CO2, H2O, 2C8H18, 25O2, 8CO2, 9H2O, phases, physical state, solid, liquid, gas, aqueous, coefficients, combustion reactions, moles and stoichiometry.

Answer 2

The chemical reaction is as follows:

C8H18 + 25/2O2 = 8CO2 + 9H2O

We are given the amount of octane in moles to be used in the reaction. We use this as the starting point in the calculations.

2.8 mol C8H18 ( 25/2 mol O2 / 1 mol C8H18 ) = 35 mol O2 needed. Hope this answers the question.