Enthalpy
I'm given that the heat of reaction for the combustion of ethane is -1560kJ/mol. I need to figure out how much heat is produced from 18g of ethane.
2 C2H6 + 7 O2 --> 4 CO2 + 6 H2O
Okay so I'm rough on Thermo right now, so I gave it my best shot. Could we write each molar amount from the equation as equal to the heat of reaction:
2mol ethane = -1560kJ/mol
7mol oxygen gas = -1560kJ/mol
4mol carbon dioxide = -1560kJ/mol
6mol water = -1560kJ/mol
Then could I convert the given 18g of ethane into moles and convert to the heat produced, using -1560kJ/mol as the heat converting value:
(18g ethane)/(30.07g/mol ethane) = .599mol ethane
(.599mol ethane)/(2mol ethane)*(-1560kJ/mol ethane) = -467.22kJ
Okay so my previous problem was going to be the fact that my final answer was -279.7kJ instead of -467.22kJ (my computer calculator doesn't show history so I don't know what dumb thing I did!)
However, here are the answers available:
A) -220.5kJ
B) -466.75kJ
C) 300.21kJ
D) 424.67kJ
So the right answer is B? Ethane, or 18g of ethane, releases about 467.22kJ or 466.75kJ? Or do these two values vary too much as to refute my calculations?
To determine the amount of heat produced from 18g of ethane, you correctly converted the mass of ethane to moles using the molar mass of ethane (30.07g/mol). You obtained 0.599 mol ethane.
Then, you used the given heat of reaction (-1560 kJ/mol) to find the heat produced by multiplying the molar amount of ethane by the heat of reaction. However, you made a minor error in your calculation.
The correct calculation is as follows:
0.599 mol ethane * (-1560 kJ/mol ethane) = -934.44 kJ
So the correct answer is approximately -934.44 kJ.
Out of the options provided, the closest answer is D) 424.67 kJ. This option is not exactly the same as your calculated value, which indicates that there might be a calculation error.
Make sure to double-check your calculations and keep track of the signs (positive or negative) during the calculation.