HONORS CHEMISTRY 1
UNIT 16 - Enthalpy, Entropy and Gibbs Free Energy
Date Agenda Homework
Mon
5/18
Review enthalpy, introduce entropy
powerpoint (slides 1-9), thermochemical constants
read p 312-314
worksheet
project choices due
Tues
5/19 Entropy and Gibbs Free energy (slides 10-12) worksheet
Wed
5/20
1/2 day
Practice Problems
finish problems
Thurs
5/21 Lab - predicting precipiates from Gibb's Free Energy finish lab
Fri
5/22 quest - H, S, G
HONORS CHEMISTRY 2
HONORS CHEMISTRY 3
Name ___________________________________________ Date _________________
Compute ΔHr for the following reactions:
1. 2NO(g) + O2(g) 2 NO2(g)
2. 4FeO(cr) + O2(g) 2Fe2O3(cr)
Will the entropy for each of the following be positive or negative? Explain.
3. sugar dissolving in tea
4. frost forms on a window pane
5. air pumped into a tire
6. acetone evaporates from nail polish remover
Will the entropy change for each of the following be positive or negative?
7. CaCO3(cr) CaO(cr) + CO2(g)
8. N2(g) + 3H2(g) 2NH3(g)
HONORS CHEMISTRY 4
Define Enthalpy:
Negative ∆H means –
Positive ∆H means –
What equation is used to calculate the enthalpy change for a reaction from the standard
enthalpies of formation:
Calculate the enthalpy change for the following reactions:
1. Standard enthalpies of formation are: C2H5OH(l) -228, CO2 -394, and
H2O(l) -286 kJ/mol. Calculate the enthalpy of the reaction,
C2H5OH + 3 O2 ® 2 CO2 + 3 H2O
2. Calculate the enthalpy of the reaction from the enthalpies of formation:
CH4 -75 kJ/mol, CO2 -394, and H2O(l) -286 kJ/mol.
CH4 + 2 O2 = CO2 + 2 H2O
Define Entropy:
Negative ∆S means –
Positive ∆S means –
HONORS CHEMISTRY 5
Predict which of the following processes will lead to an increase in the entropy of the
system?
1) N2(g) + 3H2 (g) 2 NH3(g)
2) H2O(l) H2O(g)
3) CaCO3(s) CaO(s) + CO2(g)
4) NH4NO3(s) + H2O(l) NH4+ (aq) + NO3
- (aq)
What equation is used to calculate the entropy change for a reaction from the standard
entropies of formation:
Calculate the entropy change for the following reactions using your thermodynamic
properties table:
1) N2(g) + 3H2 (g) 2 NH3(g)
2) H2O(l) H2O(g)
Define Gibbs Free Energy:
Negative ∆G means –
Positive ∆G means –
What equation is used to calculate Gibbs free energy change for a reaction from the
thermodynamic properties table:
HONORS CHEMISTRY 6
Calculate the Gibbs free energy change for the following reactions using your
thermodynamic properties table:
1) Calculate the free energy change for the combustion
of methane, CH4(g), under standard conditions. The chemical reaction is
CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g)
2) Calculate the free energy change for the combustion
of methane, CH4(g), under standard conditions. The chemical reaction is
HCl(g) + NaOH(cr) NaCl(cr) + H2O(l)
HONORS CHEMISTRY 7
HONORS CHEMISTRY 8
HONORS CHEMISTRY 9
Name _________________________________________ Date _________________
Lab Calculations:
x
1. Write the balanced equation for the following:
a) sodium iodide and potassium nitrate
b) determine if a precipitate will form
*Calculate the ∆G for product #1:
*Will product #1 precipitate? Why or why not?
*Calculate the ∆G for product #2
*Will product #2 precipitate? Why or why not?
**Does your data support or reject your calculation?
HONORS CHEMISTRY 10
2. Write the balanced equation for the following:
a) sodium sulfate and barium nitrate
b) determine if a precipitate will form
*Calculate the ∆G for product #1:
*Will product #1 precipitate? Why or why not?
*Calculate the ∆G for product #2
*Will product #2 precipitate? Why or why not?
**Does your data support or reject your calculation?
HONORS CHEMISTRY 11
