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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