Calorimetry
Calorimetry is the measurement of heat changes. The quantity of heat required to change the
temperature of a substance depends on:
1) __________________________________________________________________
2) _________________________________________________________________
3) _________________________________________________________________
(types of atoms, molecules, and IMFs)
The quantity of heat (q) can be calculated using:
Where:
c is ___________________________________________
m is ___________________________________________
T ____________________________________________
The _________________________________ is the quantity of heat required to
change the temperature of _______________________________________________. The
_____________________________________ is the quantity of heat required to change the
temperature of _________________________________. The ______________________
is the quantity of heat needed to change the temperature of _________________________.
The specific heat capacity of water is:
Example:
How much heat is needed to raise the temperature of 7.35 g of water from 21.0oC to
98.0oC?
Example:
Calculate the enthalpy change for the process in which 50.0 g of water is
converted from liquid at 10.0oC to vapour at 25oC. (see last days notes for Hvap)
Because of the First Law of Thermodynamics, the heat _______________ by a system
must be _______________ the heat lost from its _______________________ and vice
versa.
This is a useful relationship for determining the _______________________________ of a
substance.
For example:A 150.0 g sample of lead at 100.0oC is placed in 50.0 g of water at 22.0oC in an
insulated container. The final temperature of the lead-water mix is 28.8oC. What
is the specific heat capacity of lead?
The amount of heat absorbed or released during a chemical reaction can be measured with a
______________________. There are two main types of calorimeters: the
________________ calorimeter and the ___________________ calorimeter. Only coffeecup calorimeters are used in this course.
The Coffee-cup Calorimeter
The coffee-cup calorimeter is used for reactions
_____________________________________________
in general laboratory situations. In this case the entire
coffee cup and its contents are the __________________
and it has a constant ____________________ (so you are
determining qp or H). To determine H you measure the
change in temperature of the ______________________
as the reaction proceeds and then relate it to the reaction
using ________________________________________.
Example: 100.0 mL of 1.00 M HCl and 100.0 mL of 1.00 M NaOH both initially at 21.1oC are
added to a coffee-cup calorimeter and allowed to react. The temperature rises to
27.8oC. Determine the heat of neutralization for this reaction in kJ/mole H2O
formed. Is the reaction endo or exothermic? (Ignore the small heat capacity of the
stryofoam cup and assume the only thing in the system absorbing heat is the 200 mL
of solution which is almost all H2O.)
Example: 50.0 mL of 0.500 M HCl and 25.0 mL of 0.500 M NaOH both initially at 25.0oC are
added to a coffee-cup calorimeter and allowed to react. The temperature rises to
27.21oC. Calculate qsoln in J and Hrxn in kJ/mole H2O formed. Is the reaction endo or
exothermic? (Ignore the small heat capacity of the stryofoam cup and assume the
final solution has the same heat capacity and density as water.)
Calorimetry can be used to determine heat capacities, enthalpies of vaporization, enthalpies of
fusion, and enthalpies of reactions.
Silberberg: Rd p246-249 and do Q #29, 31, 33, 39, 41, 44, 46