AP Chemistry
Chapter Five Thermochemistry
Specific Heat and Calorimetry Practice Problems
Heat Capacity (C)- the amount of heat required to raise the temperature of a given quantity of a
substance 10C
Specific Heat (ρ)- the amount of heat required to raise the temperature of 1 g of a substance 1oC
Cs(H2O) = 4.184 J/goC = 1.00 cal/goC
Calorimetry- the science of measuring heat flow based on observing the temperature change
when a body absorbs or discharges heat
q = CΔT
(ΔT = Tf - Ti)
q = m x Cs x ΔT
Problem #1
How much heat does it take to raise the temperature of 225 g of water from 25.0oC to 100.0oC?
Problem #2
What will be the final temperature if a 5.00-g silver ring at 37.0oC gives off 25.0 J of heat to its
surroundings?
Problem #3
A 23.9-g sample of iridium is heated to 89.7oC and then dropped into 20.0 g of water in a
calorimeter. The temperature of the water rises from 20.1oC to 22.6oC. Calculate the specific
heat of iridium.
Problem #4
Suppose we mix 50.0 mL of 1.0 M HCl at 25.0oC with 50.0 mL of 1.0 M NaOH at the same
temperature in a calorimeter. After the reactants are mixed the temperature is observed to
increase to 31.9oC. How much energy has been released?
Assumptions:
(1) The solution volumes are additive.
(2) The NaCl(aq) is sufficiently dilute that its density and specific heat are the same as
that of pure water.
(3) The system is completely isolated. No heat escapes from the calorimeter.
(4) The heat required to warm any part of the calorimeter other than the NaCl(aq) is
negligible.
Problem #5
In a preliminary experiment, the heat capacity of a bomb calorimeter assembly is found to be
5.15 kJ/oC. In a second experiment, a 0.480-g sample of graphite (carbon) is placed in the
bomb with an excess of oxygen. The water, bomb, and other contents of the calorimeter are in
thermal equilibrium at 25.00oC. The graphite is ignited and burned. The water temperature
rises to 28.05oC. Calculate ∆H (in kJ/mol) for the reaction
C(graphite) +
O2(g)

CO2(g)