Thermochemistry Review Part 1
Definition Questions: you should be able to use or apply the following terms. Be
able to write complete definitions for,
energy
potential energy
kinetic energy
enthalpy
thermal
1.
temperature
heat
specific heat capacity
endothermic
Hess’s Law
standard state
standard heat of formation
exothermic
Law of conservation of Energy
isolated, closed, open system
The specific heat capacity of diamond is 0.5050 J/gºC. How much energy
is required to heat 25.0 g of diamond from 10.5ºC to 15.6ºC?
2. A piece of aluminum with a mass of 50g and an initial temperature of 90oC is
placed into 100mL of water at a temperature of 25oC. The temperature of
water rises to 31.30C. Determine the specific heat capacity of aluminum.
3. How much energy is absorbed by 300g of methanol, CH3OH, as it evaporates?
Given: The molar heat of vaporization is 35.3kJ/mol.
4. What is the molar enthalpy of the formation of 1mol H2SO4(l) given the
following information?
H2O(g) + SO3(g) H2SO4(l)
ΔHrxn = ___kJ
2H2(g) + O2(g)  2H2O(g)
2S(s) + 3O2(g)  2SO3(g)
H2(g) + 2O2(g) + S(s) H2SO4(l)
ΔHrxn = -484kJ
ΔHrxn = -890kJ
ΔHrxn = -814kJ
a. 4. What is the molar enthalpy of the formation of 1mol C2H6 gas given
the following information? C2H4(g) + H2(g) C2H6(g) ΔHrxn = xkJ
C2H4(g) + 3O2(g)  2CO2(g) + 2H2O(l)
2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(l)
2H2(g) + O2(g)  2H2O(l)
ΔHrxn = -1401kJ
ΔHrxn = -3100kJ
ΔHrxn = -572kJ
5. The reaction for the fermentation of glucose is Fe3O4(s) + CO(g) → 3 FeO(s) +
CO2(g)
a. Using standard enthalpies of formation, determine ΔHrxn .
b. Is this reaction endothermic or exothermic? Explain in terms of bonds
breaking/forming.
6. Answer the following questions with regards to the Heating Curve.
1)
What is happening to the average potential energy of the molecules in the
sample during section 3?
2)
As a substance goes through section (2), what happens to the distance
between the particles?
3)
What is the name of the process happening during section (2)?
4)
What would be the name of the process happening during section (2) if time
were going the other way?
5)
What is the boiling point of this substance?
6)
At what temperature would this sample finish freezing?
7)
When this substance is melting, the temperature of the ice-water mixture
remains constant because:
Heat is not being absorbed
The ice is colder that the water
Heat energy is being converted to potential energy
Heat energy is being converted to kinetic energy
a.
b.
c.
d.