What mass of ethanol,C₂H₅OH(l),must be burned to supply 500 kJ of heat? The standard enthalpy of combustion of ethanol at 298 K is -1368 kJ.mol^-1

Question

Quizplus · Accepted Answer

To solve this problem, we will use the following equation:

ΔH = q = nΔH°

Where ΔH is the heat released during the combustion of ethanol, q is the heat required (500 kJ), n is the number of moles of ethanol burned, and ΔH° is the standard enthalpy of combustion of ethanol (-1368 kJ/mol).

First, we need to calculate the number of moles of ethanol required to give off 500 kJ of heat:

q = nΔH°
500 kJ = n(-1368 kJ/mol)
n = -0.365 mol

Note that we obtained a negative value for n, which indicates that the reaction is exothermic (releases heat).

Now, we can calculate the mass of ethanol required:

m = nM
m = (-0.365 mol)(46.07 g/mol)
m = 16.8 g

Therefore, the best choice is (C) 16.8 g because it corresponds to the mass of ethanol required to supply 500 kJ of heat.

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What Mass of Ethanol,C₂H₅OH(l),must Be Burned to Supply 500 KJ