(1a) How much energy as is required to heat 120.0g of ethanol from 25 degree cel
ID: 1051449 • Letter: #
Question
(1a) How much energy as is required to heat 120.0g of ethanol from 25 degree celsius, to its boiling point and then evaporate all the ethanol?
Given the following for ethanol (l):
(1b) A bomb calorimeter with a heat capacity of 1.58 kJ/K and 1.20 kg water, is used to measure the heat of combustion from 1.000g sucrose. The tempreture increase was found to be 2.5 degrees celsius.
C12H22O11 (s) + 12O2 (g) --> 12CO2 (g) + 11H2O (l)
Use the calorimetric data to determine (i) the heat released by this reaction and (ii) the mass of sucrose that must be combusted to produce the same amount of energy as required by the ethanol in (1a)
(1c) You may assume that the heat of the reaction determined during the experiment in (1b) for the combustion of sucrose is the reaction enthalpy. Use that reaction as well as the following thermodynamic data to calculate the enthalpy of reaction for:
2CO (g) + O2(g) --> 2CO2 (g)
Explanation / Answer
(1a) Heat required to ethanol
q = 120 x 2.44 x (78.3 - 25) + 120 x 38.6 x 1000/46.068
= 116.153 kJ/mol
(1b) (i) heat released
q = 1200 x 4.184 x 2.5 + 1580 x 2.5
= 16.502 kJ
dH = 16.502 x 342.3/1 = 5648.64 kJ/mol
(ii) Heat released in part (1a) = 116.153 kJ/mol
Enthalpy of combustion of 1 mole of sucrose = -5648.64 kJ/mol
mass of sucrose to be combusted = 1 x 116.153 x 342.3/5648.64 = 7.04 kg
(1c) Enthalpy of reaction
-5648.6 = (11 x -285.83 + 12 x dHof[CO2]) - (-2226.1)
dHof[CO2] = -918.23 kJ/mol
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