2b. 12 grams of C8H18 react with oxygen to produce carbon dioxide and water. How many grams of CO2 are produced? 12.4
13.5
11.6
37.1
Other:

37.1g are produced

Explanation:

The combustion of C₈H₁₈ is:

C₈H₁₈ + 25/2O₂ → 8CO₂ + 9H₂O

Where 1 mole of C₈H₁₈ produce 8 moles of CO₂

To find the mass of CO₂ that is produced we need to convert the mass of C₈H₁₈ with molar mass. Then, with the chemical equation, we can find the moles of CO₂ and its mass, as follows:

Moles C₈H₁₈ -Molar mass: 114.2g/mol-

12g C₈H₁₈ * (1mol / 114.2g) = 0.105 moles of C₈H₁₈

Moles CO₂:

As 1 mole of C₈H₁₈ produce 8 moles of CO₂, 0.105 moles of C₈H₁₈ produce:

0.105 moles of C₈H₁₈ * (8moles CO₂ / 1mole C₈H₁₈) = 0.84 moles of CO₂

Mass CO₂ -Molar mass: 44.01g/mol-:

0.84 moles of CO₂ * (44.01g / mol) = 37.0g of CO₂ ≈

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.