Unit 10: Kinetics And Equilibrium

Transcription

1 Name Unit 10: Kinetics And Equilibrium Skills 1. Understand thery f reactin kinetics 2. Understand factrs affecting reactin rate 3. Drawing and interpreting ptential energy diagrams 4. Distinguish between end and exthermic ptential energy diagrams Unit 10: Vcabulary: Wrd Kinetics Perid 5. Defining and identifying changes in entrpy 6. Understanding and defining equilibrium 7. Understanding equilibrium thrugh Le Chatelier s Principle 8. Applying Le Chatelier with types f stressrs Cmplete thrughut unit. Due n test day! Definitin Rate Determining Step Effective Cllisin Exthermic Endthermic Ptential Energy Enthalpy Activatin Energy Activated Cmplex Frward Reactin Entrpy Chemical Equilibrium Le Chatelier s Principle Stress

2 Skill 1: Understand the thery f reactin kinetics Kinetics = study f the r at which reactins ccur A REACTION is the BREAKING and REFORMING f t make entirely new cmpunds as prducts Reactin Mechanism = STEP BY STEP PROCESS needed t make a prduct; hw yu get frm a t b (like a recipe) REACTANTS à PRODUCTS Just like when we bake a cake we must fllw directins CAN T OMIT any STEPS! CAN T CHANGE THE ORDER f the steps! CAN T OMIT any REACTANTS (ingredients) Determine whether each f the fllwing chemical reactins is an example f a slw r fast reactin. Explain why knwing this relative rate f rxn is significant. Rusting Alka seltzer in water Styrfam decmpsing Weathering f rcks Bleach remving clr WHAT DETERMINES THE RATE OF A REACTION? Time t Race!! 1. NUMBER OF STEPS = mre steps can mean a slwer reactin 2. RATE DETERMINING STEP = the f the reactin; mst imprtant factr influencing reactin rate Cllisin Thery: In rder fr are actin t ccur, reactant PARTICLES MUST and have the fllwing when ding s: * 1. Prper amunt f energy 2. Prper ALIGNMENT/DIRECTION/ORIENTATION Only when particles cllide with these tw cnditins are met will there be an COLLISION, resulting in a reactin

3 Skill 2: Identify and understand 6 Factrs Affecting Rate f Reactin: Factr Hw Rate Affected Why des it increase the rate? 1. Nature f Reactants substances react FASTER substances react SLOWER Inic = smallerà (Fewer bnds t break; Fewer Steps!) Cvalent = larger (MORE bnds t break; MORE steps): 2. Cncentratin INCREASE cncentratin, rxn rate The MORE PARTICLES in a given space, the LESS SPACE b/w particles à MORE COLLISIONS Why des cncentratin affect the rate f reactin? 3. Pressure 4. Temperature INCREASE pressure, INCREASE rxn rate (affects GASES ONLY!) INCREASE temperature, INCREASE rxn rate Increasing pressure VOLUME which DECREASES SPACE b/w particles à MORE COLLISIONS Greater SPEED à ttal COLLISIONS Greater AVERAGE KEà cllisins take place with MORE energy 5. Catalyst SPEEDS UP THE RXN WITHOUT CHANGING THE NATURE OF THE REACTANTS/PRODUCT Define Catalysis: Prvides a SHORTCUT r fr the mechanism Lwers the ACTIVATION ENERGY fr the reactin 6. Surface Area INCREASE the surface area (by making PIECES SMALLER) INCREASES the rxn rate (Hw many surfaces are there?) Increasing surface area EXPOSES MORE REACTANT PARTICLES t pssible cllisins

4 Name Kinetics: Diet Cke and Ments. Prcedure: 1. Fill the test tube three quarters with diet sda. 2. Put the white ments candy int the cap cylinder with the diet sda. Start recrding time nce ments is drpped int test tube and recrd yur bservatins. Stp timer nce the reactin stps. 3. Pull the lever and RUN! 4. Recrding time nce ments is drpped int test tube and recrd yur bservatins. Stp timer nce the reactin stps What is special abut white Ments that causes the sda geyser? (explain with details) 2. What is kinetics? Based n yur answer abve, explain which factr affected the rate f this reactin? Questins 1. Which ments with diet sda gave the biggest sda geyser? Explain why. 2. List tw ther factrs that affect the rate f a reactin. 3. Use ne f the factrs yu listed abve and state hw yu culd change this activity by varying a different factr. Explain the utcme.

5 Answer the fllwing based n this lab and yur knwledge f reactin rates: 1. Which event must always ccur fr a chemical reactin t take place? (1) Frmatin f a precipitate (2) Effective cllisins between reactin particles (3) Frmatin f a gas (3) additin f a catalyst t the reactin system 2. Increasing the temperature increases the rate f a reactin by (1) lwering the activatin energy (2) increasing the activatin energy (3) lwering the frequency f a effective cllisins between reacting mlecules (4) Increasing the frequency f effective cllisins between reacting mlecules 3. A 5.0 gram sample f zinc and a 50. Millimeter sample f hydrchlric acid are using in a chemical reactin. Which cmbinatin f these samples has the FASTEST reactin rate? (1) Zinc strip and 1.0 M HCl (2) Zinc pwder and 1.0M HCl (3) Zinc strip and 3.0M HCl (3) Zinc pwder and 3.0M HCl 4. What is required fr a chemical reactin t ccur? A) standard temperature and pressure B) a catalyst added t the reactin system C) effective cllisins between reactant particles D) an equal number f mles f reactants and prducts 5. Given the balanced equatin representing a reactin: 2HCl + Na2SO3 (aq) à S(s) + H2SO3 + 2NaCl (aq) (1) Activatin energy decreases (2) Frequency f effective cllisin decreases (3) Activatin energy increases (4) Frequency f effective cllisin increases 6. A student cnducts an experiment t determine hw the temperature f water affects the rate at which an antacid tablet disslves in the water. The student has three antacid tablets f the same size and cmpsitins. (A) Describe the effect f water temp n the rate f disslving (B) Explain in terms f cllisin thery, hw water temperature influence the rate f disslving

6 Skill 3: Drawing and interpreting Ptential Energy Diagrams: Ptential Energy Diagrams: Recall, we have talked abut chemical bnds having stred energy (AKA ptential energy). Fr that reasn, chemists use diagrams called Ptential Energy Diagrams t illustrate the ptential (r stred) energy changes that ccur during specific chemical reactins BARF (as in chemical bnds make me want t ) A reactin is the breaking and refrming f bnds BREAK BONDS à FORM BONDS A+BàC+D Heat f Reactin AKA ENTHALPY (ΔH) = the amunt f ENERGY LOST r GAINED thrughut a REACTION (ΔH = enthalpy) This quantity is equal t the PE OF THE PRODUCTS - PE OF THE REACTANTS. ΔH=H p -H R RECALL; Tw types f chemical reactins: 1. Exthermic: Reactins that energy. Δ H = negative value (-) energy released (n right).. A + B à C + D + energy Example: Sdium in water lts f heat (and fire!) prduced as prduct; heat felt n a test tube during a reactin 2. Endthermic: Reactins that energy. Δ H = psitive value (+) energy absrbed (n left) A + B + ENERGYà C + D Example: baking (need ven t supply heat) Table I (f the Reference Tables) tells us if particular reactins are exthermic r endthermic based n sign f the Δ H value...δ H (kj/ml) Endthermic/Exthermic 1. N2(g) + 2O2(g) à2no2(g) 2. N2(g) + 3H2(g) à2nh3(g) The * at the bttm f TABLE I tells yu all yu need t remember 3. 2NH3(g)à N2(g) + 3H2(g) Frward Reactin = reading LEFT TO RIGHT in a reactin; reactin mves tward the right A+BàC+D Reverse Reactin = reading RIGHT TO LEFT in a reactin; reactin mves tward the left A + B à C + D

7 . Vcabulary f a Ptential Energy Diagram: Ptential Energy f the Reactants: The amunt f energy that a system with (the starting pint in the graph. Ptential Energy f the Prducts: The amunt f energy that the system with. ACTIVATED COMPLEX: (The PEAK) energy pint f the reactin; this is where full f the reactants ccurs. Remember, this must happen fr the reactin t be successful. Activatin Energy: Amunt f ENERGY NEEDED TO GET A r t FORM THE ACTIVATED COMPLEX f a reactin (yu must get ver the hump in rder fr a reactin t ccur) Activatin energy f the Frward reactin: Energy needed t get ver the hump ging frward (left t right). Activatin Energy f the Reverse reactin: Energy needed t get ver the hump ging backward ( right t left). Heat f the Reactin (ΔH=H p H r )

8 Skill 4: Distinguish between End and Exthermic ptential energy diagrams ENDOTHERMIC Ptential Energy Diagrams àpositive ΔH Prduct side (t the R) always HIGHER than the reactant side (t the L) meaning that ENERGY is. EXOTHERMIC Ptential Energy Diagrams à NEGATIVE ΔH Prduct side (t the R) always LOWER than the reactant side (t the L) meaning that ENERGY is. Mst cmmn types f rxns because less energy has t be put in t get the rxn started (LOWER activatin energy) Label the fllwing: A = Ptential Energy f the Reactants B = Ptential Energy f the Prducts C = Ptential Energy f the Activated Cmplex D = Activatin energy f the Frward rxn E = Activatin Energy f the Reverse rxn F=Heat f the Reactin(ΔH=H p H r ) HOW EXACTLY DOES A CATALYST SHORTEN THE REACTION TIME NEEDED FOR A REACTION TO COMPLETE and hw d we shw it? The is lwered... OR The ACTIVATION ENERGY is decreased... OR The REACTION is shrtened. Draw the catalyzed reactin pathway n the diagram t the rightà

9 Name Ptential Energy Diagram 1. Using the graph belw please draw a reactin ptential energy diagram fr a reactin with the fllwing characteristics: Ptential Energy f Reactants = 350 kj/mle Activatin Energy f Frward Reactin = 100 kj/mle Ptential Energy f Prducts = 150 kj/mle Reactin Crdinate (X + Y Z) 2. Is the reactin frm questin #1 an endthermic r exthermic reactin? 3. Please identify the fllwing n the diagram yu created in questin #1. Place this letter abve its crrespnding line segment n the graph and the value in the adjacent clumn. Cmpnent f Ptential Energy Diagram Symbl Value Ptential Energy f Reactants Ptential Energy f Prducts Ptential Energy f Activated Cmplex Heat f Reactin Activatin Energy f Frward Reactin Activatin Energy f Reverse Reactin A B C D E F 4. Using a dtted line, shw hw the reactin ptential energy diagram wuld be altered upn the additin f a catalyst t the reactin in the graph abve. 5. If a catalyst were added, which lettered quantities, if any wuld change? 6. Hw wuld the additin f a catalyst affect the heat f reactin?

10 PE Diagram Wrksheet Write the frmula fr determining ΔH: Label the fllwing: A = Ptential Energy f the Reactants B = Ptential Energy f the Prducts C = Ptential Energy f the Activated Cmplex D = Activatin energy f the Frward rxn E = Activatin Energy f the Reverse rxn F=Heat f the Reactin(ΔH=H p H r ) ANSWER: 1. Is the frward reactin endthermic r exthermic? 2. Is ΔH psitive r negative fr the frward reactin? 3. Is the reverse reactin endthermic r exthermic? 4. Is ΔH psitive r negative fr the reverse reactin? 5. What effect des a catalyst have n a reactin in terms f activatin energy? 6. What effect des a catalyst have n a reactin in terms f reactin rate? 7. Changes in activatin energy during a chemical reactin are represented by a. 8. Which infrmatin abut a chemical reactin des a ptential energy diagram prvide? a. The xidatin states f prducts/reactants b. The average kinetic energy f the reactants/ prducts c. The change in slubility f the reactant d. The energy released r absrbed during the reactin

11 Regents Chemistry Name Table I Wrksheet Reactin CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l) ΔH (kj) Endthermic r Exthermic 2H 2 (g) + O 2 (g) 2H 2 O(g) C 2 H 5 OH(l) + 3O 2 (g) 2CO 2 (g) + 3H 2 O(l) C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(l) 4H 2 O(l) + 3CO 2 (g) C 3 H 8 (g) + 5O 2 (g) N 2 (g) + 3H 2 (g) 2NH 3 (g) CO 2 (g) C(s) + O 2 (g) NH 4 Cl(s) NH 4 + (aq) + Cl - (aq) 2CO 2 (g) + 4H 2 O(l) 2CH 3 OH(l) + 3O 2 (g) 2Al 2 O 3 (s) 4Al(s) + 3O 2 (g) *CO(g) + 1 2O 2 (g) CO 2 (g) *4NO(g) 2N 2 (g) + 2O 2 (g) 1. If yu reverse a reactin, what happens t the magnitude f ΔH? What happens t the sign? 2. If yu duble the cncentratin f the reactants and the prducts, what happens t the magnitude f ΔH? What happens t the sign? 3. If the ΔH fr a given frward reactin is psitive, will the reverse reactin be endthermic r exthermic? 4. If a given reactin is exthermic, will heat be fund n the reactants side f the equatin r the prducts side? 5. If a given reactin is endthermic, what will be the sign fr ΔH fr the reverse reactin?

12 Skill 5: Defining and identifying changes in ENTROPY (ΔS) Entrpy (ΔS): Degree f, CHAOS, DISORDER r MESSINESS in a system; nature tends t prceed t a state f GREATER entrpy, r disrder. The MORE ORDER yu have, the ENTROPY in yur system. The LESS ORDER yu have, the ENTROPY in yur system. is the mst significant factr in determining ΔS: Changing frm (s) à(l) à(aq) à (g) = INCREASED ENTROPY Draw particle diagrams t illustrate each f the fllwing phases: (s) (l) (aq) (g) *Entrpy when a cmpund is brken dwn. *Entrpy when a cmpund is created and bnds are frmed. NOTE: If there is n phase change, cunt up the # mlecules n each side RULE: # mlesê = ENTROPY ê = -ΔS, AND If # mles é = ENTROPY é = +ΔS) Fr the fllwing determine if there is an increase, decrease, r n change in entrpy 1. 2KClO3(s) à2kcl(s) + 3O2(g) 2. H 2O(l) à H2O(s) 3. N2(g) + 3H2(g) à 2NH3(g) 4. NaCl(s) à Na + (aq) + Cl - (aq) 5. KCl (s) à KCl (l) 6. CO2(s) àco2(g)

13 Skill 6: Understanding and Defining Equilibrium: Equilibrium ccurs WHEN THE OF THE FORWARD REACTION EQUALS THE OF THE REVERSE REACTION in a clsed system. When equilibrium is reached, IT DOES NOT MEAN that the reactants and prducts are f equal QUANTITIES. S... DOUBLE ARROWS () instead f a single arrw. This allws us t illustrate that the reactins are prceeding in bth directins (frward and reverse). Equilibrium is which means that it is cnstantly CHANGING r FLUCTUATING Equilibrium means that reactant and prduct are CONSTANT. *Equilibrium des NOT mean that reactant and prduct cncentratins are equal.* TIME FOR BAILING BEAKERS WHO WILL BE VICTORIOUS? TYPES OF EQUILIBRIUM (all ccur in ) *IT S ALL ABOUT THE EQUAL RATES* 1. Physical Equilibrium: Equilibrium that invlves physical changes Phase Equilibrium ccurs during a PHASE CHANGE RATE f MELTING = RATE f FREEZING (sealed 0 C) RATE f EVAPORATION = RATE f CONDENSATION (sealed C) Slutin Equilibrium ccurs at a slutin s POINT RATE f DISSOLVING = RATE f CRYSTALLIZATION example: NaCl (s) ß ànacl (aq) 2. Chemical Equilibrium: f the FORWARD RXN = f the REVERSE RXN OR f BREAKING BONDS = f FORMING BONDS 1. Which statement describes a chemical reactin at equilibrium? A) The prducts are cmpletely cnsumed in the reactin. B) The reactants are cmpletely cnsumed in the reactin. C) The cncentratins f the prducts and reactants are equal. D) The cncentratins f the prducts and reactants are cnstant. 2. Given the diagram representing a clsed system at cnstant temperature: Which statement describes this system at equilibrium? a. The mass f H2O( ) equals the mass f H2O(g). b. The vlume f H2O( ) equals the vlume f H2 O(g). c. The number f mles f H2O( ) equals the number f mles f H2O(g). d. The rate f evapratin f H2O( ) equals the rate f cndensatin f H2O(g).

14 Skill 7: Understanding Equilibrium thrugh LE CHATELIER s PRINCIPLE Le Chatelier s principle explains HOW A SYSTEM AT EQUILIBRIUM WILL RESPOND TO. STRESS = Any change in TEMPERATURE, CONCENTRATION, r PRESSURE put upn an system at equilibrium When a STRESS is added t a system at equilibrium, the system will in rder t relieve that stress and reach a new equilibrium. SHIFT = an increase in the f EITHER the frward OR the reverse rxn SHIFT TO RIGHT (TOWARD PRODUCTS): Rate f FORWARD reactin INCREASES ( ) Reactants à ß Prducts *Favrs PRODUCTS SHIFT TO LEFT (TOWARD REACTANTS): Rate f REVERSE reactin INCREASES ( ) Reactants ß à Prducts *Favrs REACTANTS Skill 7a: Applying Le Chatelier with Types f Stressrs Initial Stress: Cncentratin When the cncentratin f a reactant r prduct is INCREASED, the reactin will SHIFT frm the increase (use up the excess. ADD, AWAY Example 1: 4NH 3 (g) + 5O 2 (g) ß à 4NO(g) + 6H 2 O(g) + HEAT 1. If we add H 2 O (g), the system wuld shift t the and the [NH 3 ] wuld. 2. If we add O 2 (g), the system wuld shift t the and the [NO] wuld. 3. If we add H 2 O (g), the system wuld shift t the and the [NO] wuld. When the cncentratin f a reactant r prduct is DECREASED: The reactin will SHIFT the side that has experienced the decrease in cncentratin (replaces what was taken) Take, Twards Example 2: 4NH 3 (g) + 5O 2 (g) ß à4no(g) + 6H 2 O(g) + HEAT 1. If we remve xygen, the system will shift t the and the [NH 3 ] will. 2. If we remve water, the system will shift t the and the [NO] will. 3. If we remve ammnia, which cncentratin(s) will decrease? 4. If we remve NO(g), which cncentratin(s) wuld increase?

15 Initial Stress: Temperature (invlves increasing r decreasing the HEAT cmpnent f a reactin) When temperature (r HEAT) is decreased: Take, Twards The reactin will SHIFT the rxn side cntaining HEAT (in the EXOTHERMIC directin) A + B ßà C + D + HEAT Example 1: 4NH 3 (g) + 5O 2 (g) ßà 4NO(g) + 6H 2 O(g) + HEAT 1. If we remve heat, which cncentratin(s) will decrease? 2. If we remve heat, which cncentratin(s) will increase? When temperature (r HEAT) is increased: ADD, AWAY When temperature (r HEAT) is increased: The reactin will SHIFT frm the rxn side cntaining HEAT (in the ENDOTHERMIC directin) A + B + energy ßàC + D Example 2: 4NH 3 (g) + 5O 2 (g) ßà 4NO(g) + 6H 2 O(g) + HEAT 3. If we added heat, which cncentratin(s) will decrease? 4. If we added heat, which cncentratin(s) will increase? Initial Stress: Pressure..EFFECTS GASES ONLY!!!! INCREASE PRESSURE: rxn shifts t side with # GAS MOLECULES (r least # mles f gas) DECREASE PRESSURE: rxn shifts t side with GREATEST # GAS MOLECULES (r greatest # mles f gas) NOTE: If the rxn cntains NO GAS MOLECULES r if the rxn has the SAME # GAS MOLECULES n each side, there is NO EFFECT and NO SHIFT results frm an increase r decrease in pressure Example 1: CO 2 (g) ßàCO 2 (aq) 4. If we increase the pressure, the cncentratins f which species will increase? Example 2: N 2 (g) + 3H 2 (g) ßà 2NH 3 (g) 1. If we increase the pressure, in which directin will the equilibrium shift? (Cunt Mles) 2. If we increase the pressure, the cncentratin f which species will increase initially? 3. If we decrease the pressure, the cncentratin f which species will decrease initially? 4. If we decrease the pressure, the cncentratin f which species will increase initially?

16 Practice: Chemical System: 2SO3 + heat ßà 2SO2 (g) + O2 (g) a) Stress: Increasing Temperature: a. Reactin will shift Cncentratin f SO3 b. Rate f frward reactin Cncentratin f SO2 c. Rate f reverse reactin Cncentratin f O2 b) Stress: Increasing Pressure: a. Reactin will shift Cncentratin f SO3 b. Rate f frward reactin Cncentratin f SO2 c. Rate f reverse reactin Cncentratin f O2 b) Stress: Decreasing Pressure: a. Reactin will shift Cncentratin f SO3 b. Rate f frward reactin Cncentratin f SO2 c. Rate f reverse reactin Cncentratin f O2 Chemical System: 3H2(g) + N2 ßà 2 NH3 (g) + heat a) Stress: Increasing Temperature: a. Reactin will shift Cncentratin f H2 b. Rate f frward reactin Cncentratin f N2 c. Rate f reverse reactin Cncentratin f NH3 b) Stress: Decreasing temperature a. Reactin will shift Cncentratin f H2 b. Rate f frward reactin Cncentratin f N2 c. Rate f reverse reactin Cncentratin f NH3 c) Stress: Adding NH3: a. Reactin will shift Cncentratin f H2 b. Rate f frward reactin Cncentratin f H2 c. Rate f reverse reactin Cncentratin f NH3 Chemical System: BaSO4(s) ßà Ba 2+ (aq) + SO4 2- (aq) a) Stress: Adding Ba(NO3)2 (s) a. Reactin will shift Cncentratin f Ba 2+ b. Rate f frward reactin Cncentratin f SO4 2- c. Rate f reverse reactin b) Stress: Adding Ba(NO3)2 (s) a. Reactin will shift Cncentratin f Ba 2+ b. Rate f frward reactin Cncentratin f SO4 2- c. Rate f reverse reactin c) Stress: Remving SO4 2- a. Reactin will shift Cncentratin f Ba 2+ b. Rate f frward reactin Cncentratin f SO4 2- c. Rate f reverse reactin

17 Name Le Chatelier s Principle Match the change t the equilibrium system belw with the letter f the apprpriate respnse. Each letter can be used nce, mre than nce, r nt at all. 2SO2(g) + O2(g) ßà 2SO3(g) 1) O 2 is added t the reactin 2) SO 3 is remved frm the reactin 3) SO 3 is added t the reactin a) The equilibrium shifts t the right b) The equilibrium shifts t the left c) there is n change in the equilibrium 4) The pressure is increased 5) H2(g) + I2 (g) + 53 kj ßà 2 HI (g) What happens if: a. Increase Temperature: Shifts t the, [HI], [H2], [I2] b. Increase [H2 (g)]: Shifts t the, [HI], [I2] c. Increase [HI (g)]: Shifts t the, [H2], [I2] d. Decrease Pressure: 6) PCl5 (g) + heat ßà PCl3 (g) + Cl2(g) What happens if: a. Adding Cl2: Shifts t the, [PCl5], [PCl3] b. Increasing Pressure: Shifts t the, [PCl5], [PCl3], [Cl2] c. Lwering Temperature: Shifts t the, [PCl5], [PCl3], [Cl2] d. Remving PCl3: Shifts t the, [PCl5], [PCl2] 7) Fr the fllwing reactin, what will ccur if pressure is increased? Why? 2NO2(g) ßà N2O4(g) 8) Given the reactin at equilibrium :A (g) + B (g) ßà C (g) + D (g) The additin f a catalyst will: a) shift equilibrium t the right b) shift equilibrium t the left c) increase the rate f the frward and reverse reactins d) have n effect n the rate f the frward and reverse reactins

18 9) Cnsider the equatin f the fllwing reactin at equilibrium: X + Yßà2Z + heat The cncentratin f the prduct can be increased by a) adding a catalyst b) adding mre heat t the system c) increasing the cncentratin f Y d) decreasing the cncentratin f Z 10) Cnsider the fllwing equatin: H 2(g) + Cl 2(g) ßà 2HCl (g) Which change will result in an increase in the cncentratin f chlride gas? a) decreasing the pressure n the system b) decreasing the cncentratin f HCl c) increasing the cncentratin f H2 d) increasing the cncentratin f HCl 11) Cnsider the fllwing equatin: N2(g) + O2(g) ßà2NO(g) As the cncentratin f N 2(g) increases, the cncentratin f O 2(g) will a) decrease b) increase c) remain the same d) vary directly

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20 Kinetics & Equilibrium Review Fill in the blanks using the wrd bank. Only ne wrd in the bank is used TWICE. The branch f chemistry cncerned with the rates f chemical changes is called. A chemical change in which all the reactants are in the same phase is called a(n). One in which the reactants are in different phases is called a(n). A substance that speeds up a chemical change withut being permanently altered r affecting the nature f the reactin is called a(n). The series f steps by which reacting particles rearrange themselves t frm prducts is called the. The slwest step in such a series is the. A shrt-lived, high-energy arrangement f particles that is frmed when reacting particles cllide at the prper angle with the prper amunt f energy is a(n). The minimum amunt f energy needed t frm this arrangement is called the. Because this energy is stred inside the particles, it is an example f. The reactants and the prducts f any reactin have different amunts f this kind f stred energy. The difference between these tw amunts f energy is the. The heat cntent f a substance is called its. The change in this quantity that ccurs during a chemical reactin is called the, ΔH. The sign f the quantity ΔH is psitive in the case f a(n). It is negative in the case f a(n). When frward and backward reactins ccur at the same, a state f exists. A(n) is used in an equatin t symblize this state. When cnditins such as temperature are changed, a chemical reactin is said t be placed under a(n). Under such changing cnditins, equilibrium can underg a(n) in directin that tends t cunteract the impsed changes. This generalizatin is knwn as. The measure f the randmness f a system is its.

21 1) If yu were given the ΔH value f a reactin, yu culd determine whether the reactin was exthermic r endthermic. Explain hw yu culd d s. 2) In an exthermic reactin, Hprducts will always be (larger/smaller) than Hreactants Enthalpy and Table I Lk in yur Reference Tables (Table I) and state whether the fllwing reactins are exthermic r endthermic. 3. Sdium hydrxide dissciating int a psitive sdium in and a negative hydrxide in Ex r End 1. Methane (CH 4 ) cmbining with xygen t prduce carbn dixide and water 2. Ptassium nitrate dissciating int a psitive ptassium in and a negative nitrate in 4. Carbn mnxide cmbining with xygen t frm carbn dixide 5. **A psitive lithium in cmbining with a negative brmine in t frm lithium brmide Prcess ΔH Ex r End Entrpy change 1. 2H2(g) + O2(g) à2h2o(l) 2. C(s) + O2(g)à CO2(g) 3. CO2(g) àc(s) + O2(g) 4. 2C(s) + H2(g) àc2h2(g) 5. 2H2(g) + O2(g) à 2H2O(g) 6. C6H12O6(s) + 6O2(g) à6co2(g) + 6H2O(l) 7. Br-(aq) + Li+(aq)à LiBr(s) 8. H2(g) + I2(g)à 2HI(g) 9. NaOH(s) àna+(aq) + OH-(aq) 10. 2CO2(g)à O2(g) + 2CO(g)