List Of Heats Of Combustion At 25 C
Chem_Chap17.fm Page 517 Friday, May 21, 2004 1:48 PM
Table 17.2
Heats of Combustion at 25°C
Substance
∆H (kJ/mol)
Formula
Hydrogen
H2(g)
Ϫ286
Carbon
C(s), graphite
Ϫ394
Methane
CH4(g)
Ϫ890
Acetylene
C2H2(g)
Ϫ1300
Ethanol
C2H5OH(l)
Ϫ1368
Propane
C3H8(g)
Ϫ2220
Glucose
C6H12O6(s)
Ϫ2808
Octane
C8H18(l)
Ϫ5471
Sucrose
C12H22O11(s)
Ϫ5645
Table 17.2 lists heats of combustion for some common substances. The heat of combustion is the heat of reaction for the complete burning of one mole of a substance. The combustion of natural gas, which is mostly methane, is an exothermic reaction used to heat many homes around the country.
CH4(g ) ϩ 2O2(g) ¡ CO2(g ) ϩ 2H2O(l) ϩ 890 kJ
You can also write this equation as follows.
CH4(g) ϩ 2O2(g ) ¡ CO2(g ) ϩ 2H2O(l )
⌬H ϭ Ϫ890 kJ
Burning 1 mol of methane releases 890 kJ of heat. The heat of combustion
(⌬H) for this reaction is Ϫ890 kJ per mole of carbon burned.
Like other heats of reaction, heats of combustion are reported as the enthalpy changes when the reactions are carried out at 101.3 kPa of pressure and the reactants and products are in their physical states at 25°C.
Figure 17.8 The combustion of natural gas is an exothermic reaction. As bonds in methane
(the main component of natural gas) and oxygen are broken and bonds in carbon dioxide and water are formed, large amounts of energy are released.
17.2 Section Assessment
16.
Key Concept Calorimetry is based on what basic concepts?
17.
Key Concept How are enthalpy changes treated in chemical equations?
20. Explain the term heat of combustion.
Handbook
18. When 2 mol of solid magnesium (Mg) combines
with 1 mole of oxygen gas (O2), 2 mol of solid magnesium oxide (MgO) is formed and 1204 kJ of heat is released. Write the thermochemical equation for this combustion reaction.
Group 6A Look up the important chemical reactions involving Group 6A elements. Write two examples of thermochemical equations—one describing an exothermic reaction and
Table 17.2
Heats of Combustion at 25°C
Substance
∆H (kJ/mol)
Formula
Hydrogen
H2(g)
Ϫ286
Carbon
C(s), graphite
Ϫ394
Methane
CH4(g)
Ϫ890
Acetylene
C2H2(g)
Ϫ1300
Ethanol
C2H5OH(l)
Ϫ1368
Propane
C3H8(g)
Ϫ2220
Glucose
C6H12O6(s)
Ϫ2808
Octane
C8H18(l)
Ϫ5471
Sucrose
C12H22O11(s)
Ϫ5645
Table 17.2 lists heats of combustion for some common substances. The heat of combustion is the heat of reaction for the complete burning of one mole of a substance. The combustion of natural gas, which is mostly methane, is an exothermic reaction used to heat many homes around the country.
CH4(g ) ϩ 2O2(g) ¡ CO2(g ) ϩ 2H2O(l) ϩ 890 kJ
You can also write this equation as follows.
CH4(g) ϩ 2O2(g ) ¡ CO2(g ) ϩ 2H2O(l )
⌬H ϭ Ϫ890 kJ
Burning 1 mol of methane releases 890 kJ of heat. The heat of combustion
(⌬H) for this reaction is Ϫ890 kJ per mole of carbon burned.
Like other heats of reaction, heats of combustion are reported as the enthalpy changes when the reactions are carried out at 101.3 kPa of pressure and the reactants and products are in their physical states at 25°C.
Figure 17.8 The combustion of natural gas is an exothermic reaction. As bonds in methane
(the main component of natural gas) and oxygen are broken and bonds in carbon dioxide and water are formed, large amounts of energy are released.
17.2 Section Assessment
16.
Key Concept Calorimetry is based on what basic concepts?
17.
Key Concept How are enthalpy changes treated in chemical equations?
20. Explain the term heat of combustion.
Handbook
18. When 2 mol of solid magnesium (Mg) combines
with 1 mole of oxygen gas (O2), 2 mol of solid magnesium oxide (MgO) is formed and 1204 kJ of heat is released. Write the thermochemical equation for this combustion reaction.
Group 6A Look up the important chemical reactions involving Group 6A elements. Write two examples of thermochemical equations—one describing an exothermic reaction and