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Lecture Starts: 21:00

 

Thermodynamics, Part 2

 

Lecture: CModule13-2w

 

http://redwagontutorials.com/HandoutsC/Module13/1stOverhead26.htm

 

http://rwt.apologia.com   (Test Questions) 

 

http://redwagontutorials.com/HandoutsC/Module13/ExperimentGrade2.htm

 

http://redwagontutorials.com/HandoutsC/Module13/FormalReport2d.htm

 

http://www.science.uwaterloo.ca/~cchieh/cact/c120/heatreac.html

 

1.  In order to make the shells that house and protect them, many shellfish take solid lime (CaO) from the ocean floor and react it with gaseous carbon dioxide that has been exhaled by marine organisms.  The resulting calcium carbonate is the major component of their shell.  What is the ΔH° for this reaction?  (Use Table 13.2 in Appendix A)   _______________

 

http://redwagontutorials.com/HandoutsC/Module01/BlankPage.htm

 

Determine the chemical equation.

 

CaO (s) + CO2 à CaCO3 (s)


Table 13.2 from Appendix A:

 

ΔHo = [(1 mole) x (-1207 kJ/mole)] – [(1 mole) x (-635 kJ/mole) + (1 mole) x (-394 kJ/mole)] = - 178 kJ

 

Please note there is a mistake in the answer to OYO 13.5.  The answer above is correct!

 

2.   Ethane gas (C2H6) has also been considered as a fuel for automobiles because, like octane, it releases a lot of energy when it is burned.  How many kJ of energy are released when 250.0 grams of ethane undergo complete combustion?  (Use Table 13.2 in Appendix A)   _______________

 

http://redwagontutorials.com/HandoutsC/Module01/BlankPage.htm

Write a balanced chemical equation for the combustion of ethane:

 

2C2H6 (g) + 7O2 (g) à 4CO2 (g) + 6H2O (g)

 

Calculate the ΔH of the reaction:  (Hint: The standard enthalpy of formation on an element like O2 is zero.)

 

ΔHo = [(4 mole) x (-394 kJ/mole) + (6 mole) x (-242 kJ/mole)] - [(2 mole) x (-84.7 kJ/mole) + 0 kJ/mole] = - 2,859 kJ


Energy is a product in the reaction:

 

2C2H6 (g) + 7O2 (g) à 4CO2 (g) + 6H2O (g) + 2859 kJ


Convert to moles of ethane:

 

250.0 g C2H6 x 1 mole C2H6 = 8.31 moles C2H6

          1              30.1 g C2H6


2 moles of ethane give us 2,859 kJ of energy:

 

8.31 moles C2H6 x      2,859 kJ      = 1.19 X 104 kJ

           1                 2 moles g C2H6

 

Burning 250.0 g of ethane provides 1.19 x 104kJ of energy.

 

3.  A picture of the energy associated with a chemical reaction is called a/an what?   _______________  _______________

 

A picture of the energy associated with a chemical reaction is called an energy diagram.

 

http://redwagontutorials.com/HandoutsC/Module13/Figure13.1.htm

 

http://kentsimmons.uwinnipeg.ca/cm1504/Image141.gif

 

C2H6O (l) + H2 à C2H6 (g) + H2O (g)

 

4.  The vertical (y) axis of an energy graph provides the _______________ of the substances in the chemical reaction.

 

The vertical (y) axis of an energy graph provides the energy of the substances in the chemical reaction.

 

http://misterguch.brinkster.net/energydiagram.html

 

5.  T or F:  A reaction coordinate of zero means that the reaction has completed and all the products are formed.   ________

 

False:  A reaction coordinate of zero means that the reaction has not started and only the reactants are present.

 

6.  _______________  _______________ is the energy necessary to start a chemical reaction.

 

Activation energy is the energy necessary to start a chemical reaction

 

7.  Another name for the reaction activated complex is which of the following?

 

a.  the intermediate state

b.  the reaction midpoint

c.  the activation energy maximum

d.  all the above

 

Another name for the activated complex of the reaction is the intermediate state, the reaction midpoint, or the activation energy maximum.

 

8.  If the reactants have more energy than the products, then excess energy is released and the energy diagram relates that the reaction was what?   _______________ 

 

If the reactants have more energy than the products, then excess energy is released and the energy diagram relates that the reaction was exothermic.

 

http://authors.ck12.org/wiki/images/a/a5/BioI-02-03-01.jpg

 

9.  T or F:  The difference between the vertical (y) position of the products and the vertical (y) position of the reactants is the “ΔH” of the reaction.   ________

 

True:  The difference between the vertical (y) position of the products and the vertical (y) position of the reactants is the “ΔH” of the reaction.

  

10.  The activation energy is represented by the difference between the energy of the _______________ and the energy of the ______________  ____________.

 

The activation energy is represented by the difference between the energy of the reactants and the energy of the intermediate state.

 

http://www.matter.org.uk/schools/content/reactions/BondActivation.html

 

11.  A chemical reaction is just the rearrangement of what in the molecules that make up the reactants?   _______________  _______________

 

A chemical reaction is just the rearrangement of valence electrons in the molecules that make up the reactants.

 

http://www.visionlearning.com/library/module_viewer.php?mid=54&l=&c3=

 

12.  In order for rearrangement of electrons to occur, they must be given enough energy to overcome which of the following?

 

a.  the attraction that they feel toward each other

b.  the repulsion that they feel toward each other

c.  their Monday morning blahs

d.  their overnight sleepover fatigue

 

In order for rearrangement of electrons to occur, they must be given enough energy to overcome the repulsion that they feel toward each other.

 

http://www.800mainstreet.com/7/0007-004-reac_rate2.htm

 

13.  T or F:  If the energy of the reactants is lower than the energy of the products, then the reaction is endothermic.   ________

 

True:  If the energy of the reactants is lower than the energy of the products, then the reaction is endothermic.  Energy had to be added to the reaction so that the reactants could form products.

 

http://redwagontutorials.com/HandoutsC/Module13/Figure13.2.htm

 

14.  The First Law of Thermodynamics states that energy cannot be _______________ or _______________; it can only change form.

 

The First Law of Thermodynamics states that energy cannot be created or destroyed; it can only change form.

 

http://www.opencollege.com/simsim/php/ResourceManager.php?cmd=get_view&catID=1481&resID=1410&outcat=1

 

15.  A measure of the disorder that exists in any system is termed what?   _______________

 

Entropy is a measure of the disorder that exists in any system.

 

http://en.wikipedia.org/wiki/Entropy

 

16.  Entropy (S) is measured in which of the following units?

 

a.  grams/dL x oC

b.  liters/ Kg x K

c.  Joules/mole x oF

d.  kJ/mole x K

 

Entropy (S) is measured in Joules/mole x K; kcals/mole x K; or kJ/mole x K.

 

17.  T or F:  A large entropy indicates a highly ordered state.   ________

 

False:  A large entropy indicates a highly disordered state.

 

http://mooni.fccj.org/~ethall/entropy/entropy.htm

 

18.  The Second Law of Thermodynamics states that the entropy of the universe must always either _______________ or remain the same.  It can never _______________.

 

The Second Law of Thermodynamics states that the entropy of the universe must always either increase or remain the same.  It can never decrease.

 

19.  T or F:  To a large extent, the Second Law of Thermodynamics determines what types of events are possible in nature and what types of events are not possible.   ________

 

True:  To a large extent, the Second Law of Thermodynamics determines what types of events are possible in nature and what types of events are not possible.

 

http://www.science.uwaterloo.ca/~cchieh/cact/applychem/entropy.html

 

20.  Which state of matter has the highest entropy?

 

a.  solid

b.  liquid

c.  gaseous

d.  California

 

The gaseous state of matter has the highest entropy because the molecules (or atoms) that make up a substance move the most freely and quickly.

 

http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter17/Text_Images/FG17_08.JPG

 

21.  The entropy of a system increases with increasing what?   _______________

 

The entropy of a system increases with increasing temperature.

 

http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter17/Text_Images/FG17_07.JPG

 

22.  Which has greater entropy: (1) one car in a parking lot or (2) the parking lot at a Dallas Cowboy home football game?   ________

 

The entropy of a system increases as the matter it contains increases; therefore, the parking lot at a Dallas Cowboy home football game would have the greater entropy.

 

http://upload.wikimedia.org/wikipedia/commons/b/b1/Cowboys_Stadium_screen.jpg  

 

23.  If the entropy of the universe must always either increase or stay the same, then the change in entropy of the universe must be either _______________ or _______________.

 

If the entropy of the universe must always either increase or stay the same, then the change in entropy of the universe must be either zero or positive:  ΔS > 0.

 

24.  T or F:  In general, the side of the reaction that contains the most molecules (or atoms) in the gas phase has the lowest entropy.   ________

 

False:  In general, the side of the reaction that contains the most molecules (or atoms) in the gas phase has the highest entropy.  Next would be the side with the most liquids molecules.  Finally, solids would have the least entropy and the side with the largest number of solid molecules has the highest entropy, if all of the molecules are in the solid phase.

 

http://myweb.cwpost.liu.edu/vdivener/notes/solid-liquid-gas.gif 

 

25.  Determine the sign of ΔS for the following reactions:

 

a.  C2H402 (aq) + NaHCO3 (s) à NaC2H3O2 (aq) + H2O (l) + CO2 (g)    ΔS is _______________

 

This reaction has one gas molecule on the products side of the equation and none on the reactants side.  This means that the products have more entropy than the reactants, so ΔS is positive.

 

b.  2AgNO3 (aq) + Mg(OH)2 (aq) à 2AgOH (s) + Mg(NO3)2 (aq)        ΔS is _______________

 

This reaction has no molecules or atoms in the gas phase, thus we must look at the liquid (or aqueous) phase.  There are three molecules in the aqueous phase on the reactants side and only one molecule in the aqueous phase on the products side.  As a result, ΔS is negative.

 

26.  All substances, even _______________, have an absolute entropy. 

 

When calculating ΔS, the S of an element is not zero.  All substances, even elements, have an absolute entropy. 

 

27.  Consider the following reaction: 

 

CaO (s) + CO2 à CaCO3

 

Using Table 13.3 in Appendix A, the calculated value for ΔSo for the reaction would be which of the following? 

 

a.  - 159 J/mole K

b.  + 159 J/mole K

c.  - 340 J/mole K

d.  + 340 J/mole K

 

ΔSo = [(1 mole x (92.9 J/mole K)] – [(1 mole) x (38.2 J/mole K) + (1 mole) x (214 J/mole K)] = - 159 J/K)

 

http://redwagontutorials.com/HandoutsC/Module01/BlankPage.htm

 

28.  T or F:  The Second Law of Thermodynamics makes evolution impossible.   ________

 

False:  To make evolution consistent with the Second Law of Thermodynamics, the organism’s surroundings would have to become more disorganized so that the decrease in entropy generated by the organism’s evolution could be offset by the other changes.  The Second Law of Thermodynamics relates to the universe as a whole; not just one creature’s change in it.  The net effect is that the total entropy of the universe is always in agreement with the Second Law.

 

http://www.christiananswers.net/q-eden/edn-thermodynamics.html    

 

29.  Theories like Neo-Darwinism and Punctuated Equilibrium are/are not (circle one) consistent with the Second Law of Thermodynamics.

 

Theories like Neo-Darwinism and Punctuated Equilibrium are not consistent with the Second Law of Thermodynamics.  The Second Law does not disprove these theories.  It just means that no one has come up with the proper mechanism to demonstrate their validity.

 

30.  If a chemical reaction has a negative ΔH, the entropy of the surroundings _______________.    

 

If a chemical reaction has a negative ΔH, the entropy of the surroundings increases.  If a chemical reaction has a positive ΔH, it absorbs energy from its surroundings, decreasing its entropy.

 

31.  In the formula for Gibbs Free Energy (ΔG = ΔH – T x ΔS), T is the temperature of the surroundings in what?   _______________

 

In the formula for Gibbs Free Energy (ΔG = ΔH – T x ΔS), T is the temperature of the surroundings in Kelvin.

 

http://www.chem1.com/acad/webtext/thermeq/TE4.html 

 

32.  T or F:  The Gibbs Free Energy actually can tell us whether or not a reaction is consistent with the Second Law of Thermodynamics.   ________

 

True:  The Gibbs Free Energy actually can tell us whether or not a reaction is consistent with the Second Law of Thermodynamics.

 

http://library.thinkquest.org/C006669/data/Chem/thermodynamics/gibbs.html

 

33.  If the Gibbs Free Energy value is consistent with the Second Law of Thermodynamics, then the reaction is which of the following?

 

a.  free

b.  undecided

c.  spontaneous

d.  not spontaneous

 

If the Gibbs Free Energy value is consistent with the Second Law of Thermodynamics, then the reaction is spontaneous.  If the Gibbs Free Energy value is not consistent with the Second Law of Thermodynamics, then the reaction is not spontaneous, and the reaction cannot occur.

 

When ΔG < 0, then the reaction is consistent with the Second Law and is thus spontaneous.  If ΔG > 0, then the reaction cannot proceed, because it violates the Second Law of Thermodynamics.

 

34.  A reaction is exothermic (has a negative ΔH) and also has a positive ΔS, it will always be a _______________ reaction.

 

A reaction is exothermic (has a negative ΔH) and also has a positive ΔS, it will always be a spontaneous reaction.  If ΔH is positive and ΔS negative, ΔG will always be positive.

 

http://users.stlcc.edu/gkrishnan/entroandfenergy.html

 

35.  Reactions that are endothermic and have a negative ΔS will never be what?   _______________

 

Reactions that are endothermic and have a negative ΔS will never be spontaneous.

 

36.  T or F:  ΔG is state function; therefore, Hess’s Law can be used to calculate ΔG.   ________

 

True:  ΔG is state function; therefore, Hess’s Law can be used to calculate ΔG.  Be sure to work On Your Own questions 13.11 and 13.12.