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The heat of combustion is a difference of enthalpy (DH) observed in the chemical

ID: 940337 • Letter: T

Question

The heat of combustion is a difference of enthalpy (DH) observed in the chemical reaction between one mole of a substance (the fuel) and oxygen (the oxidizer), forming gas carbon dioxide and water vapor. The following chart shows the enthalpy of combustion, in certain temperature for ethane, propane, butane, pentane and hexane.

According to the graph can estimate that: (Justify your answer, explaining the reason for this school alternative)

(A) 1000 kcal are released in the combustion of 1 mole of hexane.

(B) 650 kcal are necessary for the combustion of 1 mole of butane.

(C) 700 kcal are necessary for the combustion of 2 moles of ethane.

(D) 500 kcal are released in combustion 3 propane moles.

(E) 1600 kcal are released in combustion 2 pentane moles.

300 6 -400 S 500 th -600 E -700 o -800 E -900 1000 4 Número de Átomos de Carbono

Explanation / Answer

A:- With increasing number of carbon atoms in fuels ( hydrocarbons ) the heat combustion increases, hence 1 mole hexane releases high amount of energy ( i.e.1000 kcal ), where as 1 mole of ethane releases low amount of energy ( i.e. 350 kcal).