2st cot spontenous and non-spontenous_powerpoint - Copy - Copy (1).pptx

gen chem 2 lesson

1. GOOD DAY, GUYS..

2. Learning Competency: Predict the spontaneity of a process based on entropy. (STEM_CG11CT-IVa-b-140)

3. Spontaneous Process and Entropy

4. Chemical Thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics.

5. Thermodynamics is a scientific discipline that deals with the interconversion of heat and other forms of energy. It has traditionally recognized three fundamental laws: First Law - Energy of the universe is constant. “Energy can be converted from one form to another, but it can never be created nor destroyed”; Second Law - Entropy of universe increases. “The entropy of the universe increases in a spontaneous process and remains unchanged in the equilibrium process”; and Third Law - At absolute zero, the entropy of a perfect crystal is 0. “The entropy of the perfect crystalline substance is zero at the absolute zero of temperature (T = 0, K = -273.150C).”

6. Spontaneous process as stated in the second law is a physical or chemical change that occurs by itself. A process that takes place without energy from an external source. It is the time-evolution of a system which releases free energy and it moves to a lower, more thermodynamically stable energy state.

7. If heat flows into surroundings (exothermic) the random motion of the molecules in the surroundings increases. Thus, the entropy of the surroundings increases. Entropy is a thermodynamic quantity that is a measure of randomness and disorder. It measures how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy. It tells whether a process or chemical reaction can occur. The connection between entropy and the spontaneity of a reaction is expressed by the second law of thermodynamics.

8. The change in entropy for a given amount of heat absorbed also depends on temperature. If the temperature of the surroundings is high, the molecules are already quite energetic. Therefore, the absorption of heat from an exothermic process in the system will have relatively little impact on the motion of the molecules and the resulting increase in entropy of the surroundings will be small. However, if the temperature of the surroundings is low, than the addition of the same amount of heat will cause a more drastic increase in molecular motion and hence a larger increase in entropy.

9. Consider the phase changes illustrated bellow.

10. The entropy of a substance increases (ΔS > 0) as it transforms from a relatively ordered solid, to a less-ordered liquid, and then to a still less-ordered gas. The entropy decreases (ΔS < 0) as the substance transforms from a gas to a liquid and then to a solid.

11. What did you observe?

12. Activity 1. COMPARE ME! Compare the pictures in each set.

13. 1. What can you say about the pictures? ________________________________ ___________________________________________________________________________ 2. How do you compare the pictures? __________________________________ ___________________________________________________________________________ 3. Which one is more spontaneous? Why? _____________________________ ___________________________________________________________________________

14. Uphill and Downhill Skiing

15. 1. What can you say about the pictures? ________________________________ ___________________________________________________________________________ 2. How do you compare the pictures? __________________________________ ___________________________________________________________________________ 3. Which one is more spontaneous? Why? _____________________________ ___________________________________________________________________________

16. Activity 2. I’M EVERYWHERE! A spontaneous process is one that takes place without energy from an external source. For a chemical reaction to be spontaneous, it should proceed as written (from left to right), without an input of energy. An endothermic process absorbs heat from the surroundings and has a positive value, whereas an exothermic process release heat to its surroundings and has a negative value.

17. Examples of reactions Combustion of methane CH4 + 2O2 → 6CO2 + 2H2O Δ H0 = -890.4 kJ/mol 2. Acid-base neutralization H+(aq) + OH-(aq) → H2O(l) ΔH0 = -56.2 kJ/mol Both of these reactions are very exothermic and are not reversible.

18. 3. Solid to liquid phase transition of water H2O(s) → H2O(l) ΔH0 = 6.01 kJ/mol 4. Dissolution of ammonium nitrate in water NH4NO3(s) → NH4+(aq) + NO3-(aq) ΔH0 = 6.01 kJ/mol Ice melting above 0C and ammonium nitrate dissolving in water are both spontaneous process yet endothermic.

19. Directions: Classify the given situations below whether the process is spontaneous or non-spontaneous. Rusting of iron in moist air Drying of leave 3. Decaying of radioisotopes 4. Dissolving of salt 5. Oxidation of gold 6. Radioactive atom splits up 7. Spoilage of food 8. Dissolution of sand in water 9. Burning of chlorine 10. Fireworks

20. Activity 3. I’M A PART OF YOU! Entropy, S, is the thermodynamic quantity that is a measure of how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy. It is a quantity that is generally used to describe the course of a process, that is, whether it is a spontaneous process and has a probability of occurring in a definite direction, or a non-spontaneous process and will not proceed in the defined direction, but in the reverse direction.

21. Activity 3. I’M A PART OF YOU! Most processes are accompanied by entropy change. The following are processes that lead to an increase in entropy of the system Process Order → Disorder Melting Solid → Liquid Vaporization Liquid → Vapor Dissolving Solute → Solution Heating System at T1 → System at T2 (T2 > T1)

22. Entropy change examples: 1. Gas in balloon spreads out into room and deflates but never a balloon spontaneously filled with air. ►The molecules of gas at a high pressure always spread to lower pressure regions. 2. Hot coffee in a room gets cooler and the heat spreads out into the room, but never a cold cup of coffee being spontaneously warmed up. ►Heats always goes from high temperature into cooler regions.

23. Entropy change examples: The spreading out of more concentrated molecules and the spreading out of more concentrated energy are changes from more order to more random.

24. FACT OR BLUFF! Directions: Write Fact on the blank if the condition illustrates entropy and write Bluff if does not illustrates entropy. __________ 1. Oxidation of nitrogen _____________2. Sublimation of mothballs _____________3. Reduction of silicon _____________4. Lighting of candles _____________5. Flow of water up hill __________6. Digestion of food _____________7. Boiling water for tea _____________8. Flow of heat from a cold body to a hot body _____________9. Diffusion of LPG _____________10. Making popcorn

25. Activity 4. WORD SEARCH Directions: Search and encircle the important terms being described in the sentences below. Words can be forward, backward, vertical, horizontal, or diagonal.

26. Activity 4. WORD SEARCH 1. The scientific discipline that deals with the interconversion of heat and other forms of energy. 2. A process of a physical or chemical change that occurs by itself. 3. The measure of randomness and disorder. 4. Process that gives off heat to the surroundings. 5. Process that absorbs heat from the surroundings. 6. The value of the product during endothermic process. 7. The value of the product during exothermic process. 8. The change of phase from solid to liquid. 9. The change of phase from liquid to gas. 10. The change of phase from solid to gas.

27. Activity 4. WORD SEARCH

28. Activity 5. CORRECT ME IF I’M WRONG! Directions: Write TRUE if the statement is correct but if it’s false, change the underlined word or group of words to make the whole statement true.

29. Activity 5. CORRECT ME IF I’M WRONG! ____________1. If heat flows into the surroundings, the random motion of the molecules in the surroundings decreases . ____________2. In a chemical reaction, the heat change is positive if the heat product is lower than the heat reactant. ____________3. The heat change is negative if the heat product is greater than the heat reactant. ____________4. Spontaneous process is reversible reaction. ____________5. Entropy changes occur when gas molecules inside the LPG tank escape and spread out into room.

30. Activity 5. CORRECT ME IF I’M WRONG! ____________6. Heat flows from hotter objects to a colder one is a spontaneous process. ____________7. Burning of fuel is an example of endothermic reaction . ____________8. Coffee granules dissolve faster in hot water than in cold water. ____________9. Melting of ice cream left on top of a table is an example of exothermic reaction. ____________10. For a chemical reaction to be spontaneous, it should proceed without an input of energy.

31. SUM UP! What characterize a spontaneous process? _____________________________ 2. How does spontaneity apply to a chemical reaction?______________________________ 3. How do entropy changes occur?______________________________ 4. How is hot object in an open area gets cooler?___________________________________

32. GOOD AFTERNOON, GUYS…….

33. THE SECOND LAW OF THERMODYNAMICS Chemical Thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics.

34. THE SECOND LAW OF THERMODYNAMICS The Second Law of Thermodynamics deals with entropy , the quantity that measures how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy. It tells whether a process or chemical reaction can occur. The connection between entropy and the spontaneity of a reaction is expressed by the second law of thermodynamics. This law says that when energy changes from one form to another form, or matter moves freely, entropy (disorder) in a close system increases.

35. THE SECOND LAW OF THERMODYNAMICS The change in entropy for a given amount of heat absorbed also depends on temperature. If the temperature of the surroundings is high, the molecules are already quite energetic. Therefore, the absorption of heat from an exothermic process in the system will have relatively little impact on the motion of the molecules and the resulting increase in entropy of the surroundings will be small. However, if the temperature of the surroundings is low, then the addition of the same amount of heat will cause a more drastic increase in molecular motion and hence a larger increase in entropy.

36. THE SECOND LAW OF THERMODYNAMICS The significance of this law is that, it tells us about the direction of heat transfer and what process are impossible even if they satisfy the first law.

37. THE SECOND LAW OF THERMODYNAMICS Examples are: engine can’t have an efficiency of 100%, a fridge can’t work without a power supply. Another example is a human body. We eat food (high temperature reservoir). The coffee eventually cools down showing that the heat only flows from high temperature to low temperature without the aid of any external agent. A cold object in contact with a hot one never gets colder, transferring heat to the hot object and making it hotter furthermore. Mechanical energy, such as kinetic energy, can be completely converted to thermal energy by friction, but the reverse is impossible.

38. THE SECOND LAW OF THERMODYNAMICS Because the universe is made up of the system and the surroundings, the entropy change in the universe ( ΔSuniv ) for any process is the sum of the entropy changes in the system ( ΔSsys ) and in the surroundings ( ΔSsur ).

39. THE SECOND LAW OF THERMODYNAMICS ΔSuniv = ΔSsys + ΔSsur > 0 Process is spontaneous ΔSuniv = ΔSsys + ΔSsur = 0 Process tends not to occur, equilibrium is attained ΔSuniv = ΔSsys + ΔSsur < 0 Reverse process occurs spontaneously

40. Activity 1. IT’S GETTING HOTTER IN HERE! Directions: Calculating Entropy Changes in the system: Standard Entropy of Reaction, ΔS0rxn . Data needed in calculating the entropy change: 1. Suppose that the system is represented by the following reactions: aA + bB → cC + dD 2. The standard entropy of reactions ΔS0rxn is given by the difference in standard entropies between the products and the reactants. ΔS0 = ΣnS0 (products) - ΣnS0 (reactants) 3. • Where m and n are the stoichiometric coefficients in the reaction. Δ S0rxn = [cS0(C) + dS0(D)] - [aS0(A) + bS0(B)]

41. Note: Standard entropy values: J/K mol; 1atm; 250C

42. From the standard entropy values in the Thermodynamic Data table, calculate ΔS0 for the following reaction. Study Me! H2(g) + I2(s) 2HI(g) Step 1. Write the standard entropy below each formula H2(g) + I2(s) → 2HI(g) From the table, S0(J/ K.mol ) 130.6 116.7 206.3

43. From the standard entropy values in the Thermodynamic Data table, calculate ΔS0 for the following reaction. Study Me! H2(g) + I2(s) 2HI(g) Step 2. Using the equation for the standard entropy of reaction ΔS0 = ΣnS0 (products) - ΣnS0 (reactants) = [(2) S0 HI] - [(1) S0 H2 + (1) S0 I2]

44. From the standard entropy values in the Thermodynamic Data table, calculate ΔS0 for the following reaction. Study Me! H2(g) + I2(s) 2HI(g) Step 3. Substitute the entropy values. = [(2) (206.3)] - [(1) (130.6) + (1) (116.7)] = [412.6] - [247.3] Δ S0 = +165.3 J/K-mol

45. From the standard entropy values in the Thermodynamic Data table, calculate ΔS0 for the following reaction. Study Me! H2(g) + I2(s) 2HI(g) Step 3. Substitute the entropy values. = [(2) (206.3)] - [(1) (130.6) + (1) (116.7)] = [412.6] - [247.3] Δ S0 = +165.3 J/K-mol

46. SOLVE ME! 1. Determine S for the reaction: SO3(g) + H2O(l) H2SO4(l)

47. SOLVE ME! 2. Calculate S for the reaction SO2(s) + NO2 SO3(g) + NO(g)

48. SOLVE ME! 3. Calculate S at 250C for the reduction of a given these absolute entropies: 2PbO(s) + C(s) 2Pb(s) + CO2(g)

49. Activity 8. PREDICT ME! General rules in predicting entropy change of the system: 1. If the reaction produces more gas molecules than it consumes, ΔS0 is positive. 2. If the total number of gas molecules diminishes, ΔS0 is negative. 3. If there is no net change in the total number of gas molecules, ΔS0 may be positive or negative, but will be relatively small numerically.

50. Activity 8. PREDICT ME!

51. Activity 8. PREDICT ME! Directions: Predict whether the entropy change of the system in each of the following is positive or negative.

52. Activity 8. PREDICT ME! Directions: Predict whether the entropy change of the system in each of the following is positive or negative.

53. Activity 9. CROSSWORD PUZZLE Directions: Solve the crossword using the clues.

54. Activity 9. CROSSWORD PUZZLE Directions: Solve the crossword using the clues.

55. Regional Senior High School (SHS) Mass Training of Grade 11 Teachers on Academic s June 20 - 25, 2016

56. THE SECOND LAW OF THERMODYNAMICS GIBBS’ FREE ENERGY According to the second law of thermodynamics, a spontaneous reaction increases the entropy of the universe: that is Δ𝑆𝑢𝑛𝑖𝑣 > 0. In determining the direction of the Δ𝑆𝑢𝑛𝑖𝑣 , calculation of Δ𝑆𝑠𝑦𝑠 and Δ𝑆𝑠𝑢𝑟𝑟 are both necessary. The mathematical expression is given by

57. THE SECOND LAW OF THERMODYNAMICS The equation expressing only the properties Δ𝐻𝑠𝑦𝑠𝑎𝑛𝑑 𝑇Δ𝑆𝑠𝑦𝑠 can now be used as a criterion in determining if a spontaneous reaction occurs. For convenience, multiply both sides of the equation in equation 3 by -1 and change the > sign with <:

58. THE SECOND LAW OF THERMODYNAMICS Equation 4 says that as a reaction proceeds at a constant pressure and temperature, the reactants forms products and if the changes in H and S of the system is less than zero, the process is spontaneous. The relationship between H and S was introduced by the American Physicist J. Willard Gibbs. He introduced another thermodynamic quantity known as the Gibb’s free energy (G) or simply free energy. The mathematical relationship is given by

59. THE SECOND LAW OF THERMODYNAMICS where G is the free energy, H is the enthalpy, T is the temperature and S is the entropy. All quantities pertain to the system only. The change in free energy ( Δ𝐺 ) of a system for a constant-temperature process is given by

60. THE SECOND LAW OF THERMODYNAMICS this context, free energy is the energy available to do work. The conditions for spontaneity and equilibrium at constant temperature and pressure in terms of Δ𝐺 are as follows: • Δ𝐺 < 0, the reaction is spontaneous in the forward direction • Δ𝐺 > 0, the reaction is non-spontaneous (spontaneous in the opposite direction) • Δ𝐺 = 0, the system is at equilibrium

61. THE SECOND LAW OF THERMODYNAMICS EXAMPLES 1. For farmers, the reaction between nitrogen gas and hydrogen gas is very important because the resulting product is ammonia which is very essential in plant production such as corn and palay. What is the free-energy change, Δ𝐺 , for the following reaction at 250C? N2(g) + H2(g) NH3(g)

62. THE SECOND LAW OF THERMODYNAMICS SOLUTION Write the balanced chemical equation and placed below each formula the values of Δ𝐻 and Δ𝑆 . Use Table 1 to locate for the needed values.

63. THE SECOND LAW OF THERMODYNAMICS SOLUTION

64. THE SECOND LAW OF THERMODYNAMICS Determine the spontaneity of the reaction Δ𝐺= −33.45𝑘𝐽 which is lesser than 0. This means that the reaction is spontaneous in the forward direction.

65. THE SECOND LAW OF THERMODYNAMICS 2. Methane is one of the components of LPG. So every time you cook your food in your gas stoves, you are burning methane. Calculate Δ𝐺 for the following reaction at 250C. CH4(g) + O2(g) CO2(g) + H2O(g)

66. THE SECOND LAW OF THERMODYNAMICS Write the balanced chemical equation and placed below each formula the values of Δ𝐻 and Δ𝑆 . Use Table 1 to locate for the needed values. CH4(g + 2O2(g) CO2(g) + 2H2O(g)

67. THE SECOND LAW OF THERMODYNAMICS Use equation 8 and 9 to compute for the Δ𝐻0 and Δ𝑆0

68. THE SECOND LAW OF THERMODYNAMICS Use equation 6 to compute for the free energy Determine the spontaneity of the reaction Δ𝐺= −803.8𝑘𝐽 which is lesser than 0. This means that the reaction is spontaneous in the forward direction.

69. THE SECOND LAW OF THERMODYNAMICS STANDRAD FREE ENERGY CHANGE The standard-free energy of reaction ( Δ𝐺𝑟𝑥𝑛𝑜) is the free-energy change for a reaction when it occurs under standard-state conditions, when reactants in their standard states are converted to products in their standard states. The standard states are as follows: for pure liquids and solids, 1 atm pressure; for gases, 1 atm partial pressure; for solutions, 1 M concentrations. The temperature of interest is 250C or 298 K. To calculate for Δ𝐺𝑟𝑥𝑛𝑜 , we start with the equation a A + b B c C + d D

70. THE SECOND LAW OF THERMODYNAMICS where m and n are stoichiometric coefficients. 𝑮𝒇𝒐 is the standard free-energy of formation of a compound. It is the free-energy change that occurs when 1 mole of the compound is synthesized from its elements in their standard states.

71. THE SECOND LAW OF THERMODYNAMICS EXAMPLES 3. Calculate the standard free-energy changes for the following reactions at 250C. a. CH4(g) + O2(g) CO2(g) + H2O(g)

72. THE SECOND LAW OF THERMODYNAMICS a. Solution • Write the balanced chemical equation and placed below each formula the values of Δ𝐺 . Use Table 1 to locate for the needed values. CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

73. THE SECOND LAW OF THERMODYNAMICS Use equation 10 or 11 to compute for the free energy Determine the spontaneity of the reaction Δ𝐺= −818.0𝑘𝐽𝑚𝑜𝑙 which is lesser than 0. This means that the reaction is spontaneous in the forward direction.

74. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. MgO(s) Mg(s) + O2(g)

75. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. 2 . H2(g) + Br(l) HBr(g)

76. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. 3. C2H6(g) + O2(g) CO2(g) + H2O

77. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. b. MgO(s) Mg(s) + O2(g) Δ𝐺= 1139.2𝑘𝐽𝑚𝑜𝑙 which is greater than 0. This means that the reaction is non-spontaneous.

78. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. C. H2(g) + Br(l) HBr(g) Δ𝐺= −106.4𝑘𝐽𝑚𝑜𝑙 which is lesser than 0. This means that the reaction is spontaneous in the forward direction.

79. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. D. C2H6(g) + O2(g) CO2(g) + H2O Δ𝐺= −33.45𝑘𝐽 which is lesser than 0. This means that the reaction is spontaneous in the forward direction.

80. QUIZ#1

81. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. 1 . CH4(g + O2(g) CO2(g) + H2O(l)

82. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. 2. C2H6(g) + O2(g) CO2(g) + H2O

83. THE SECOND LAW OF THERMODYNAMICS QUIZ#1 Calculate the standard free-energy changes for the following reactions at 250C. 3. H2(g) + Br(l) HBr(g)

84. QUIZ#1 _______is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics?

85. QUIZ#1 ________is a scientific discipline that deals with the interconversion of heat and other forms of energy?

86. QUIZ#1 ______ is a physical or chemical change that occurs by itself?

87. QUIZ#1 _____ thermodynamic quantity that is a measure of randomness and disorder?

88. QUIZ#1 _____ absorbs heat/energy in the surroundings?

89. QUIZ#1 _____ release heat/energy in the surroundings?

90. QUIZ#1 Burning of wood is an example of_____________?

91. QUIZ#1 According to the second law of thermodynamics, the entropy of the universe__________________?

92. QUIZ#1 The relationship between H and S was introduced by the American Physicist __________________?

93. QUIZ#1 Important components in determining entropy of the universe __________________?

94. QUIZ#1 Δ𝐺 < 0, the reaction is __________________?

95. QUIZ#1 Δ𝐺 > 0, the reaction is __________________?

96. QUIZ#1 Δ𝐺 = 0, the system is __________________?

97. QUIZ#1 Mathematical equation in determining Gibbs free energy __________________?

98. QUIZ#1 Write equation number 8 __________________?

99. QUIZ#1 16-20. complete name of your chemistry teacher ________?