RATE REACTION

A. ObjectivesStudy the effect of surface area of solid reactant, concentration, temperature, and catalyst toward the rate reaction.B. TheoryChemical kinetics, also known asreaction kinetics, is the study ofratesof chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about thereaction's mechanismandtransition states, as well as the construction of mathematical models that can describe the characteristics of a chemical reaction. In 1864,Peter WaageandCato Guldbergpioneered the development of chemical kinetics by formulating thelaw of mass action, which states that the speed of a chemical reaction is proportional to the quantity of the reacting substances. Chemical kinetics deals with the experimental determination ofreaction ratesfrom whichrate lawsandrate constantsare derived. Relatively simplerate lawsexist forzero-order reactions(for which reaction rates are independent of concentration),first-order reactions, andsecond-order reactions, and can be derived for others. In consecutive reactions, therate-determining stepoften determines the kinetics. In consecutive first-order reactions, asteady stateapproximation can simplify therate law. Theactivation energyfor a reaction is experimentally determined through theArrhenius equationand theeyring equation. The main factors that influence thereaction rateinclude: thephysical stateof the reactants, theconcentrationsof the reactants, thetemperatureat which the reaction occurs, and whether or not anycatalystsare present in the reaction. The rate of a chemical reaction is the relationship in the change of the amount of a reactant or product with respect to time. For the general reaction, 2 A + B C + D, one way to describe the rate of the reaction would be the change (increase) in the concentration of D with respect to time. Another way to express it would be the rate of change (decrease) of A with respect to time. These two expressions of the rate can be related through a negative sign and a fraction of based on A disappearing twice as fast as D.

We know from everyday experience that the change include that the change included the chemical change take place with different speed. The time required to achieve a change is influence by varios factor, than the same changes can take place with the different speed condition. In this experiment it will be investigated how reaction rate is influence by surface area, concentration of solution, temperature and catalyst.According to the theory of collision, the reactants will react if they collide intensively. Concentration affect the number of collision occured. The greater the concentration of reactants, more frequent collisions between them, so that the greater possibility of product formation. Similarly, if the reactant is solid, the surface area will accelerate the reaction.The reaction can run by the effective collision, so not all collisions result a reaction. Effective collisions requires precise posotioning and considerable energy. Carbon and oxygen though already in contact, will not form carbon dioxyde without the heat. The minimum enegy required for reacting is called activation energy (Ea). Reaction with high Ea is difficult or run slow. Ea can be lowered using catalyst.The rate reaction will increase sharply if the temperature is raised. An increase in temperature mainly caused the increase of Ea of molecules bounded, and it is important for incesing the number of collision

C. Apparatus and Reagent1. Apparatus :a. Analytical balancee. Graduated cylinderb. Burner methylatedf. Baeker glassc. Test tubeg. Erlenmeyer flaskd. Test tube clamph. Stopwatch 2. Reagent :a. HCl 1,5 M solutionf. H2C2O4 0,05M solutionb. Marble g. MnSO4 0,18M solutionc. Na2S2O3 0,15 M solutionh. KMnO4 0,01 M solutiond. H2SO4 0,5M solutioni. FeCl3 0,5M solutione. H2O2 3%j. MnO2 powderD. Procedur

E. Observation Data1. The surface area of rectantsThe occured reaction :MarbleReaction time (s)

Pieces1336,81

Powder30,37

2. Concentration of reactants[HCl] variated + [Na2S2O3] constantNa2S2O3 0,15 M (mL)Volume (mL)Concentration of HCl (M)t (s)1/t (s-1)

HCl 1,5 Mwater

25501,519,00,053

25320,923,00,043

25140,336,00,028

Graph 1. The relation between 1/t and HCl concentration

[HCl] constant + [Na2S2O3] variatedHCl1,5 M (mL)Volume (mL)Concentration of Na2S2O3 (M)t (s)1/t (s-1)

Na2S2O3 0,15 Mwater

52500,1519,00,053

52050,1222,00,045

515100,950,00,020

510150,658,00,017

55200,3134,00,007

Graph 2. The relation between 1/t and concentration Na2S2O3

3. The temperature of reactionThe occured rection :Solution A + H2SO4 + Solution BTime until the solution clear (s)

Without heating105

After heating6

4. CatalystH2O2 solutionObservation

Without addition of Lany substancesCold, colorless

After addition of FeCl3Warm, any bubble, Fast reaction, yellow-brown

After addition of MnO2Warm, any bubble, fast reaction, grey

5. AutocatalystThe occured reaction :Test tubeH2C2O4 (drop)H2SO4 0.5 M (drop)MnSO4 0.5 M (drop)KMnSO4 (drop)t (s)

1420150

14202135

14203155

14204192

14205204

14206197

14207208

14208353

14209428

142010566

142011231

142012646

242112

Graph 3. The relation between t and drop of KMnO4

F. Discussion1. The surface area of reactantIn this experiment, we react marble and chloride acid. Aim of this experiment is to show how the affect of surface area of reactant toward the rate reaction. The marble which used in this experiment in two shape, there are pieces and powder. Both of them have same weight. The result shows that time until raction finished with marble in pieces shape is 1336,81 seconds and reaction with marble in powder is 30,37 seconds.This experiment saw that the surface area of reactant with different shape affect the rate reaction.with the same weight, the time until reaction finished are different. Marble in powder shape is react faster than in pieces shape. It is because the surface area in powder is wider than the surface area pieces shape.when there is compound in solid phase, than it shared into little shape. That is true that the shape is more little but there is addition of surface area in that compound. If the suface area is wider, the rate reaction is faster because the collision between reactant molecules are greater and it makes efective collision.2. Concentration of reactantTo looking for the affect of concentration of reactant in rate reaction, we did two variated reactions between sodium thiosulphate and chloride acid. First, concentration of HCl is variated. In the other hand, concentration of sodium thiosulphate is constant. Second, concentration of sodium thiosulphate is variated. In the other hand, concentration of HCl is constant.The first experiment saw that if the concentration of HCl is higher, the rate reaction is faster. In the second experiment saw if the concentration of Na2S2O3 is higher, the rate reaction is faster too.Both of experiment saw that concentration is greater, the rate reaction is faster. It is because so greater the concentration of substances, so the capability to do collision will occured higher than the substances with liquid concentration. The amout of collision occured wil caused efective collisionis higher too. The efective collision with higher intention will makes the greater rate reaction.3. Temperature of reactionThis experiment to prove the affect of temperatureof reaction in reaction. The time until reaction finish between H2C2O4 0,05M and KMnO4 0,01 M in acid condition (there is H2SO4) and room temperature is 105 seconds. After the solution is heated, the time until reaction finish is 6 seconds.Both of the experiment saw that the time which needed to react will faster after the solution is heated. It is because the kinetic energy of molecules wil greater when the temperature of reactant is higher. So the collision between molecules will occured is more often. It will occured more efective and the rate reaction will faster.4. Catalyst A catalyst is a substance that accelerates the rate of a chemical reaction at a certain temperature, without any changes or unused by the reaction itself. In this experiment, a catalytic role in the reaction but not as a reactant or a product. The catalyst allows the reaction to go faster or enable the reaction at lower temperatures due to the changes that triggered the reagent. Catalysts provide a choice of pathways with lower activation energy. The catalyst reduces the energy required for the course of the reaction. Catalysts are sometimes involved in the reaction but did not undergo a permanent chemical change, in other words at the end of the reaction the catalyst will be found again in the same form and amount as before the reaction. By decreasing the activation energy at the same temperature the reaction can take place more quickly.5. Autocatalyst The occured reaction is 3H2SO4 + 2KMnO4 + 5H2C2O4K2SO4 + 2MnSO4 + 10CO2 + 8H2O. Autocatalyst is a catalyst That it is product of reaction can be as catalyst. In this reaction, the autocatalyst is MnSO4. More MnSO4 that producted, the rate reaction is faster. But our data this experiment are different from the theory. It caused by some mistake like : Practican is not carefully in count the time Practican is not carefully when watch the color change in solution from pink become transparentThis experiment saw that with additional an autocatalyst can make fast the rate reaction because autocatalyst can decreasing the activation energy (Ea). G. Conclusion1. The rate reaction is inflence by some factor, there are surface area of solid reactant, concentration, temperature, catalyst, etc.2. More wider the surface area of solid, the rate reaction will be faster.3. More greaer the concentration, the rate reaction will be faster.4. More higher the temperature, the rate reaction will be faster.5. Catalyst can make fast the rate reaction by decreasing the actaivation energy.6. Autocatalyst is a matter from the result of reaction and it can be catalyst to.7. Autocatalyst can make fast the ate reaction and combine with other catalyst.H. Suggestion1. Practican should know the procedures before do the experiment and do the experiment carefully.2. In the experiment to prove affect of surface area toward rate reaction, mass of pieces and powder marble should be weighed not the estimation.3. In the experiment autocatalyst should not too much so that not spend the time.4. All of member in group must working together so that the experiment will done well.

I. Bibliography

Question1. The surface area of reactanta. Which is wider surface area (with the same weight), marble in pieces or powder?b. What are the effect of surface area of marble toward the rate reaction?2. Concentration of reactanta. What are the effect of the concentration of HCl to the rate of reaction of marble and Na2S2O3?b. What are the influence of Na2S2O3 concentration to the rate of reaction?c. Draw a graph showed The relationship of 1/t and sodium thiosulfate concentration?3. The temperature of reactiona. What are the effect of temperatur toward on the reaction between potassium permanganate with oxalic acid and sulphuric acid?b. Write down the occured reaction? 4. Catalysta. CuCl2 and FeCl3 are containing Two kinds of ions, cation and anions, which ion work as a catalyst? b. In this reaction, H2O2 decomposes to form H2O and O2, whether the catalyst is also changing as a result of a reaction?5. Autocatalysta. Why is the rate of reaction on the first droplets of a solution of KMnO4 in the first tube is shower when compared with the second tube?b. What is the effect of manganese (II) sulfate in the reaction which takes place on the tube?

Answer1. The surface area of reactanta. Marble in powder is wider than in pieces.b. By increasing the surface area, the collision between marble and HCl molecules is easier. As a consequence the reaction rate of dissolving powder is faster than pieces.2. Concentration of reactiona. Affecting concentration HCl solution to rate rection is the higher concentration, so the rate reaction is faster.b. Affecting concentration Na2S2O3 solution to rate reaction is the higher concentration, so the rate reaction is faster.c. The relation between 1/t and concentration Na2S2O3

3. The temperature of reaction a. Reaction between pottasium permanganate, oxalic acid, and sulphuric acid which heated, the rate reaction become fasterthan withiut heating. This concern shows that if temperature increased, so the rate reaction become faster because more and more many molecules which reach activation energy and more and more high the quantity of collision of molecules. b. The reaction :2KMnO4 + 5H2C2O4 + 3H2SO4K2SO4 + 2MnSO4 + 8H2O + 10 CO22K+ + 2MnO4- + 16H + 5C2O22- + 3SO42-2K+ + 3SO42- + 2Mn2+ + 8H+ + 8OH- + 10 CO24. Catalyst a. Cation works as catalyst in this reaction.b. No. Catalyst is gain again in final of reaction.5. Autocatalyst a. The rate reaction on the first droplets is slower than second droplets because the first tube has little catalyst and the second tube has higher catalyst than first tube. S, the first tube is slower when compared with the second tube.b. In the additional of MnSO4 in the second tube, it makes the rate reaction in the second tube become faster than the firs tube because MnSO4 is autocatalyst. It is a matter which its product reaction used as catalyst. Beside that, MnSO4 in the second tube is higher than the fisrt tube.