Pad 2:30 PM a session.masteringchemistry.com Exercise Mastering Chemistry Exerci

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Pad 2:30 PM a session.masteringchemistry.com Exercise Mastering Chemistry Exercise T If 3.395 g of ethanol C2 H5 OH(1) is burned completely in a bomb calorimeter at 298.15 K, the heat produced is 100.4 kJ Part A Calculate H Express your answer to four significant figures and include the combustion for ethanol at 298.15 K appropriate units. Hcombustion-L alueUnits Submit GiveUP Part B Calculate Hf of ethanol at 298.15 K Express your answer to four significant figures and include the appropriate units. H = alue Units Submit Give U Continue

Explanation / Answer

A)

Hcombustion = Qcombustion / mol of ethanol

mol = mass/MW = 3.395/46

mol of ethanol = 0.07380

Q = 100.4 kJ

HRcomb = -100.4/0.07380

HCombustion = 1360.433 kJ/mol

B)

for ethanol

HRxn = Hproducts - HReactatns

C2H5OH + O2 = CO2 + H2O

C2H5OH + O2 = 2CO2 + H2O

C2H5OH + O2 = 2CO2 + 3H2O

C2H5OH + 3O2 = 2CO2 + 3H2O

HRxn = ( 2CO2 + 3H2O) - (C2H5OH + 3O2 )

-1360.433 = (2*-393.5 + 3*-285.8) - (C2H5OH +3*0)

C2H5OH  = (2*-393.5 + 3*-285.8) + 1360.433  

C2H5OH  = -283.967 kJ

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