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# Hydrocarbons, compounds containing only carbon and hydrogen, are important in fuels. The heat of combustion of cyclopropane, C3H6, is 499.8 kcal/mol. ?

## Write a balanced equation for the complete combustion of cyclopropane How much energy is released during the complete combustion of 446 grams of cyclopropane ? _ kcal

Mar 7, 2018

We write the stoichiometric combustion reaction...

#### Explanation:

${C}_{3} {H}_{6} \left(g\right) + \frac{9}{2} {O}_{2} \left(g\right) \rightarrow 3 C {O}_{2} \left(g\right) + 3 {H}_{2} O \left(l\right) + \Delta$

...and here $\Delta {H}_{\text{combustion}}^{\circ} = - 499.8 \cdot k c a l \cdot m o {l}^{-} 1$.

And so we interrogate the molar quantity of cyclopropane...

$\frac{446 \cdot g}{42.08 \cdot g \cdot m o {l}^{-} 1} = 10.6 \cdot m o l$...and given the formation of stoichiometric carbon dioxide and water....we get....

$\Delta = 10.6 \cdot m o l \times 499.8 \cdot k J \cdot m o {l}^{-} 1 \equiv 5297.3 \cdot k J$...

Mar 7, 2018

Balanced chemical combustion equation:

$2 {C}_{3} {H}_{\text{6(g)" + 180_"2(g)" -> 6CO_"2(g)" + 6H_2O_"(l)}}$


$10614.8$ kCal released during combustion of 446 grams of ${C}_{3} {H}_{6}$.

#### Explanation:

Set up balanced equation:

$2 {C}_{3} {H}_{6} + {180}_{2} \to 6 C {O}_{2} + 6 {H}_{2} O$


Use dimensional analysis:

$\left(446 g {C}_{3} {H}_{6}\right)$ $\left(\frac{1 m o l {C}_{3} {H}_{6}}{42 g}\right)$ $\left(\frac{2 m o l {C}_{3} {H}_{6}}{1 m o l {C}_{3} {H}_{6}}\right)$ $\left(\frac{499.8 k C a l}{m o l {C}_{3} {H}_{6}}\right)$ $=$

$10614.8 k C a l$