FindingEnthalpy.notebook
August 05, 2012
Finding delta H for various reactions
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FindingEnthalpy.notebook
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EXERCISES
In Exercises 10 and 11, make the approximations:
■ the heat capacity of all solutions is that of water (4.2 J K–1 g–1)
■ the heat capacity of the container (beaker) is negligible
■ there are negligible heat losses to the surroundings
■ the density of all solutions is 1.0 g/mL.
NaOH + HCl ­­­­­­­­­­­ NaCl + H2O
XS acid is used. The amount of product is determined by the limiting reagent NaOH. 0.005 mol present
Q = mc delta T
m = 75g or 0.075kg
change in temp = 0.9oC
Q = 75 x 4.2 x 0.9oC
Q = 283.5 J this is for 0.005mol of NaOH
56700J per mol
or 56.7kJ mol­1
exothermic so this ans = ­56.7KJ mol­1
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FindingEnthalpy.notebook
August 05, 2012
What is heat of neutralization?
this is the heat liberated when one mole of water is produced between and acid­base reaction Read more: http://wiki.answers.com/Q/What_is_heat_of_neutralization#ixzz22dhd1icC
http://www.chm.davidson.edu/vce/calorimetry/HeatofNeutralization.html
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FindingEnthalpy.notebook
August 05, 2012
KI + Pb(NO3)2 ­­­­­­­­­­­­­­­­­ PbI2 + 2KNO3
This is a precipitation reaction and balancing above is NOT COMPLETE.
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FindingEnthalpy.notebook
August 05, 2012
KI + Pb(NO3)2 ­­­­­­­­­­­­­­­­­ PbI2 + 2KNO3
1. Identify the reagent in XS.
2. Which reagent runs out first?
3. Find the number of moles present.
4. Find amount of heat released for this mass of mixture
Find final value adjusting for 1 mole of Pb2 +
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FindingEnthalpy.notebook
August 05, 2012
KI + Pb(NO3)2 ­­­­­­­­­­­­­­­­­ PbI2 + 2KNO3
1. Identify the reagent in XS.
2. Which reagent runs out first?
3. Find the number of moles present.
4. Find amount of heat released for this mass of Find final value adjusting for 1 mole of Pb2 +
mixture
0.01moles of lead ions present
Q = mc delta T
80g x 4.2 x 2.6 = 873.6J
= 87360J per mol
­87.4KJ mol­1
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FindingEnthalpy.notebook
August 05, 2012
change?
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FindingEnthalpy.notebook
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7.6 HEAT OF COMBUSTION
The molar heat of combustion of a substance is the heat liberated when 1 mole
of the substance undergoes complete combustion with oxygen at standard
atmospheric pressure with the final products being carbon dioxide gas and
liquid water
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