Question #bf193

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Answer 1 · 2015-03-27T18:42:20

You must burn 110.5 g of octane.

You know that 1 mol of octane liberates 5471 kJ of heat.

To liberate 5290 kJ of heat, the mass of octane must be

$5290 cancel("kJ") × (1 cancel("mol C₈H₁₈"))/(5471 cancel("kJ")) × "114.23 g"/(1 cancel("mol C₈H₁₈")) = "110.5 g C₈H₁₈"$

Answer 2 · 2015-03-27T18:42:31

$110.2g$ is required.

$C_8H_18+12(1)/(2)O_2rarr8CO_2+9H_2O$

$DeltaH_c=-5471"kJ"$

$M_r=114$

So $5471"kJ"$ is produced by $114g$

So $1"kJ"$ is produced by $(114)/(5471)g$

So $5290"kJ"$ is produced by $(114)/(5471)xx5290=110.2"kJ"$