Answer:
= -522.5\,\, kJmol^{-1}
Explanation:
Firstly, we know that 0.36 g of ethanol burned, so we can convert this into a number of moles.
Using a formula triangle to calculate the number of moles of ethanol in a 0.36 gram sample
Secondly, we can use \Delta H=cm\Delta T to calculate the enthalpy change in the experiment described in the question (ie when 0.008 moles of ethanol is burned).
\Delta H=cm\Delta T = 4.18 x 0.2 x 5
= 4.18 kJ
Lastly, we can use the enthalpy change for the experiment in the question to calculate the enthalpy of combustion (ie when one mole of ethanol is burned).
0.008\,\,moles\,\,ethanol = 4.18kJ
1\,\,mole\,\,ethanol = \frac{1}{0.008} \times 4.18
= -522.5\,\, kJmol^{-1}
