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Chemistry 104 B/D
Discussion Section Worksheet
Discussion Section #4
Key Ideas from Lecture #4:
q = q:
Let’s review constant pressure calorimetry using a heating curve:
Constant volume calorimetry:
Hess’s Law:
Let’s think about these concepts for a bit.
..
In this class we have looked at both constant pressure and constant volume calorimetry.
What
values do these different forms of calorimetry allow us to determine?
In what type of reactions
are the values of
Δ
H and
Δ
E closest to each other?
Why would you want to use one type of
calorimetry over another experimentally?
For these questions, it may be helpful to consider the equations:
Δ
E = q + w
w =  P
ext
Δ
V
Δ
H = q (constant pressure)
Problems:
Hour Exam I, Spring 2007, #12
You completely combust one (1) piece of paper in a bomb calorimeter (C = 6.93 kJ/
o
C) and find
that the temperature of the bomb apparatus increases by 71.4
o
C.
You look up the
Δ
E of
combustion for paper and find that
Δ
E
comb
= 2787 kJ/mol.
How much did the sheet of paper
weigh (assuming a MW of paper of 180.18 g/mol)?
Stuck?
First, try to understand what the problem is asking for.
Next, list all the important
information that you know (including equations that may be useful).
Try to determine the best
way for you to solve the problem, then solve the problem.
Does the answer make sense?
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 Spring '08
 Harwood
 Calorimetry

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