00:02
Hi there, in this question we are given this balanced chemical equation for the combustion of ethanol and we are given the delta h of reaction as negative 1366 .7 kilojoules.
00:15
That negative sign tells us it is exothermic, so energy is released.
00:21
We want to know how much energy is going to be released if we burn 24 .77 grams of the ethanol.
00:32
Okay, well to answer this question then, what we are going to need to do is to convert from grams of ethanol to moles of ethanol.
00:45
We can do that by using its molar mass, which is the mass of one mole of the substance in grams.
00:51
And we get the molar mass from the periodic table by adding together the individual masses.
00:55
So the mass of two carbon plus six hydrogen and one oxygen.
00:59
Once we have moles, we can convert to our amount of energy, or heat in this case.
01:11
Because we see from our balanced equation, the coefficient in front of the ethanol is not written, so it is understood it is a one.
01:19
So we know that one mole of the ethanol releases that energy, negative 1366 .7 kilojoules.
01:33
Okay, so this will give us our heat in kilojoules...