Rates of reaction experiments Essay Example for Free

Rates of reaction experiments Essay I was planning to observe each reaction for 10 minutes and was able to do so because the reactions started getting slow after a while I had a few problems during my experiment. The size of the chips was not exactly the same, each group was made up of chips of approximately equal sizes and this is not exactly accurate. In stirring the experiment we had to be careful of stirring it evenly and not aggravating the reaction. The experiment could have been improved in various ways. Using beads of limestone can solve the problem of unequal size of particles. Using a magnetic stirrer can be used solve the problem of uneven stirring of reactants. The use of a more accurate scale helps in solving the problem of reading off measurements from the measuring cylinder. Drawing the curves of best fit was an accurate step I took. My graphs helped in proving my aim, A distinctive trend is shown in the graph as clearly show that small particles react faster than large particles. I was interested in this experiment when I first started. I was interested in seeing changes in the reactants at the end of the reaction. I was very satisfied when I found out that my predictions were correct. The effect of concentration on Rate of Reaction Aim In this experiment my aim is to find out whether rate of reaction increases when concentration in a reaction is increased. Word equation Sodium Thiosulphate + Hydrochloric Acid Sodium Chloride + Sulphur Oxide + Water + Sulphur Chemical formula Na2S203(aq) + 2HCl(aq) 2NaCl(aq) + SO2(g) + H2O(l) + S(s) This reaction usually produces a white precipitate, which is the Sulphur and a putrid smell, which is the sodium chloride. Two main factors are needed in this reaction for it to succeed. The first, being that the reactant particles must meet and collide. If no collisions take place then the reaction cannot happen. Secondly the reaction must have enough energy to form a product. The activation energy is the most minimum amount of energy that is needed for a product to be formed. Once the solution has become totally opaque the reaction is complete. This means all the reactant has been used up and the reaction is complete. We can see this if a piece of card with a cross on it is placed under the conical flask. Once the cross is completely obscured from vision, if looking through the conical flask to the bottom, the reaction has taken place. The time it takes for this to happen is measured as the rate of reaction. Purpose of this experiment The purpose of this experiment is to record how long it takes for the cross under the conical flask to disappear under different concentrations. We have chosen sodium thiosulphate to use in different concentrations from a range of 10 ml to 40 ml. I believe 4 concentrations will be a sufficient amount although more can be taken to further the investigation Apparatus needed for this experiment are: Conical Flask stopwatch White tile marked With X . Chemical needed for the experiment are: 1) Sodium thiosulphate 2) Water (distilled) 3) Hydrochloric Acid Fair test I will need to keep in order to get correct results and to do this I need to keep in mind a list of variables, which are: The temperature of apparatus should not change Try to control the surface area of the reaction Try and judge accurately when the X mark is disappearing Fixed amount of Sodium thiosulphate and water should be added Prediction I predict that when the concentration of the acid is raised, the rate of the reaction will increase. This is because, when the concentration of acid is higher, more acid particles are present in a given volume of the solution, therefore, more acid particles are available to collide with HCl particles. This consequently increases the chances of successful collisions (those resulting in a reaction) occurring. As the collision theory states, the more collisions that occur in a period of time, the faster the rate of the reaction. This is because the reaction only occurs when Hydrochloric acid and Sodium thiosulphate particles collide each other Safety. As safety is the number one priority in this experiment, many safety precautions were taken to make it as safe as possible   Goggles were worn to make sure that eyes were protected.   Hair and loose jewelry were tied up.   A safe distant was kept in case of any spillages.   Any spillages on clothes and skin were rinsed thoroughly immediately. Any spillages on work surfaces and on the floor were mopped up with a damp paper towel. As Sulphur Dioxide can appear to be a hazardous gas, windows and doors were opened to keep maximum ventilation in the room. Method 40 ml of Sodium thiosulphate should be poured in the flask Then 10 ml of HCl should be poured into another flask 10 ml of distilled water should be poured onto another flask Put a tile containing an X mark under the sodium thiosulphate flask Then mix all these 3 chemicals into one such as pour the 10 ml of water and 10 ml of HCl onto the flask containing sodium thiosulphate. As soon as the reaction starts put the stopwatch on After we saw the reaction between started forming white precipitate which made the X mark look dimmer and dimmer to finally no X mark. As soon as the X mark is not seeable stop the stopwatch and record the time Everytime we finish a reaction we had to use another flask Everytime we start another reaction the concentration of sodium thiosulphate we decrease it by 10 ml and increase water by 10 ml During the experiments the amount of |Hydrochloric acid always remains the same at 10 ml The steps are the same for every new reaction on this experiment whether if the concentration even changes Preliminary work Before conducting a real experiment I will do a Preliminary test to check whether the experiment will work out. I have used the same method as shown above and theses are the results I obtained Volume of sodium thiosulphate (ml) water (ml) Hydrochloric acid (ml) Time it takes for X to vanish 3secs Experiment diagram Results The table below shows the results of my real experiment. The experiment was done for 3 times to get the average time taken which can make it even more accurate Na2S2O3 (Ml) H2O (Ml) Volume of HCl (Ml) Trial 1 Time taken (Seconds) Trial 2 Time taken (Seconds) Trial 3. Time taken (Seconds) Average Time taken (Seconds) 40 ml 10 ml 10 ml   000 Conclusion After conducting my experiment and while looking at my results I feel that my predictions were true because I predicted that when the concentration is high the reaction will be fast compared to the reaction with less concentration and same in my result I saw when sodium thiosulphate is 40 ml and water is 10ml the reaction takes 48. 83 seconds but when water is at 40 ml and sodium thiosulphate is at 10 ml the reaction takes 194. 00 seconds Analysis As you can see from the results in the section before, the graphs and recordings clearly show that the concentration does affect the rate of the reaction. As the concentration increases, the rate of reaction speeds up as well. The following graphs clearly state that where the sodium thiosulphate was most dilute, and was at the concentration of 10ml, the rate of reaction took the longest on average and in every experiment taken. The graphs also show that the rate of reaction happened the quickest when the Na2S203 was at its highest concentration. As you can see in the graph, the graph takes a negative correlation in form. The rate of reaction time starts off highest because of the low concentration. As the reactant particles are further apart and there are more spectator ions present, getting in the way of the reaction. These ions do not take part in the reaction but can slow it down as the do act as an obstruction. This makes it very hard fro collisions to take place. This prevents the reaction from happening quickly and stops the product from forming quickly. As the concentration slowly increases, the number of spectator ions decreases in the same given volume, which in the experiment is 10cm3. This makes it more likely and easier for collisions to actually occur. This being as it is, it means that the reaction happens quicker and so the products are formed quicker as well. Even though the rates of reaction for the different concentrations were all very different, the cross on the card eventually disappeared in every experiment. The cross did not really disappear though. This is just a phrase used. What really happened was that the solid Sulphur that is formed as a precipitate of the reactions, shields our view and it is an opaque substance. The Sulphur is a milky yellow colour and can be seen when emptying out the contents of the conical flask. It sometimes can leave a residue on the inside of the flask. The rate of reaction also depends on how quickly all the Sulphur is formed as an end product. This can be dependent on the concentration as well. If there are more particles in a given volume there are going to be more atoms that need to bond to make the product. Aim My aim for this coursework is see whether rate of a chemical reaction is affected by the addition of a catalyst in the reaction How a catalyst works There are many ways in which we are able to speed up the rate of reactions. A catalyst can either increase or decrease the rate of reaction. A positive catalyst lowers activation energy. The particles, therefore, need less energy to react and the process proceeds more quickly. A negative catalyst (an inhibitor) slows down the rate of a chemical reaction by doing the exact opposite. However, it is important to realize that the catalyst itself does not take place in the reaction and it is, therefore, not used up in the reaction. Below is an energy diagram showing the presence of a catalyst. The graph shows the effect of a positive catalyst on the activation energy. When you use a catalyst, there is as much catalyst at the end of the reaction as there was at the beginning. The catalyst is used over and over again. As catalysts work so fast and are used again and again, it is only necessary to have small quantities of catalyst present to make a chemical reaction go faster. Solid catalysts work by providing a surface onto which the reactant particles can attach, react, rearrange and then leave. Catalysts work in a very similar way to increasing surface area, when it comes to the rate of reaction. Catalysts are no different. If you want a solid catalyst to be as effective as possible, it should have the largest surface area possible. By putting holes in the catalyst, it will have a large surface area and be more effective at catalyzing a particular reaction than if it was just a solid lump. Apparatus needed for the experiment Delivery Tubes Test Tubes Test tube clamp Stop watch Stand Chemicals used in the experiment A) Hydrogen Peroxide B) Potato Chippings Fair Test: Fair test must be kept in mind to promote accurate results. For this reason I had to keep: The same mass for the catalyst The temperature during the experiment shouldnt change Concentration should remain the same Prediction I can predict that when the catalyst will be added to the reaction the reaction will be quicker and faster because of the collision moving faster. I predicted this because when I learnt about catalyst the fist thing that was taught to me was that catalyst increase any kind of reactions Formula Hydrogen Peroxide water + Oxygen 2H2O2 (aq) H20( l ) + O2 ( g ) Method For this experiment the catalyst we will be using is Potato. And it will be cut into pieces of 1cm The method we done our experiment is show below: 1) First we need to set up all the apparatus we need during the experiment 2) Put Hydrogen Peroxide inside the test tube and add Potato chippings (catalyst) 3) Heat the te.