Question

(b) What is the ratio of grams 8l Cu (Use the results of Example 2.3.) The standard enthalpy for selected organic compounds is given in this problem. For ea 2.8 compute the gross and net heats of combustion. (a) Propane (C,Hs);-103.8 kJ/mol (b) n-Butane (C4H10); -124.7 k/mol (c) Isobutane (C4H10);-131.6 kJ/mol (d) Ethanol (), (C2H,OH); -277.6 kJ/mol (e) Methanol (1), (CH,OH),-238.6 kJ/mol hoot of combustion for ethyl alcohol (C,H,OH) is-1,370 kJ/mol. What is its

Answer 1

For Gross heat of combusti on we need to take the water in li quid state Standard enthalpy of water in liquid state is ΔΗΗ'og,--285.8 kJ/mol For Net heat of combustion we need to take the water in gaseous state Standard enthalpy of water in gaseous state is H,10,--2418 kJ/mol Write the reaction for the combusti on of propane as follows: Net heat- 3 co,+4AH H,0(g) = 3(-393 5) +4(-241 8)-(-1038)-5(0) kJ/mol -2043.9 kJ/mol Gross heat-3(AHco, ) + 4(M,00)-M,A-SH H,0() 3(-393.5)4(-285.8) -(-103.8)-5(0) kJmol -2219.9 kJ/mol Therefore, the net heat is 2043.9 kJ/mol and Gross heat is -2219.9 kJ/mol Write the reaction for the combustion of n-Butane as follows 13 2 410 Net heat-4AHco)+5AHH or) 13 - 4(-393.5)+5(-241.8)-(-124.7)-(0)kmol --2658.3 kJ/mol Gross heat4c5AHH -4(-393.5) +5(-285.5) -(-1247)-()kml -2876.8 kJ/mol Therefore, the net heat is -2658.3 kJ/mol and Gross heat is -2876.8 kJ/mol Write the reaction for the combusti on of isobutene as follows 13 Net heat-4[AHco.)+5AH,OE) 13 -4(-3935)+5(-241.8)-(-1316)-(0) kmol -2651.4 kJ/mol

Gross heat- 4[AHco,)+5AHH H20(t) -4-393.5) 5-285.5)-(-131.6)-0)kJ/mol =-2869.9 kJ/mol Therefore, the net heat is -2651.4 k/mol and Gross heat is -2869.9 kJ/mol Write the reaction for the combustion of ethanol as follows Net heat-2(AHco,)+ 3 AHH0( 3AH 2(-393.5)+3(-241.8)-(-277.6)-3(0) kJ/mol -1234.8 kI/mol Gross heat-2AHco. ) + 3ΙΔΗ H20() 2(-393.5) +3(-285.5) -(-277.6)-3(0) kJlmol -1365.9 kJ/mol Therefore, the net heat is -1234.8 kJ/mol and Gross heat is -1365.9 kJ/mol Write the reaction for the combustion of methanol as follows Net heat- 2(AH -(-393.5)+2(-241.8)-(-238.6)-(0)kTmol -638.5 kJ/mol Gross heat- [AHco,)+ 21AHH.0C) 33.5)2(-285.5)-(-238.6)0)kJ/mol =-725.9 kJ/mol Therefore, the net heat is -638.5 kJ/mol and Gross heat is -725.9 kJ/m ol