We must produce a piece of coursework investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. It is measured by dividing 1 by the time taken for the reaction to take place. There is five factors which affect the rate of a reaction, according to the collision theory of reacting particles: temperature, concentration (of solution), pressure (in gases), surface are (of solid reactants), and catalysts.
I have chosen to investigate the effect temperature and concentration have on a reaction. This is because they are the most practical to investigate – it would take longer to prepare a solid in powdered and unprepared form, and it is difficult to get accurate readings due to the inevitabilities of human errors, and as gas is mostly colorless it Is difficult to gauge a reaction changing the pressure, and if a substance is added to give the gas color, it may influence the outcome of the experiment.
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Similarly the use of a catalyst complicates things, and if used incorrectly could alter the outcome of the experiment. Aim: – To see the effects of a change In temperature and concentration on the rate of a reaction. The reaction that will be used Is: Sodium Theosophical + Hydrochloric Acid Nauseas (as) + CLC (as) Sodium Chloride + Water + Sulfur Dioxide + enact (as) + H2O (l) + ASS (g) + Sulfur Two series of experiments will be carried out – one changing the temperature (while everything else remains constant) and one varying the concentration (while keeping everything else constant).
Both the sodium theosophical and the Hydrochloric acid are soluble In water, so the concentration of either can be changed. However I have chosen to vary the sodium theosophical as It Is available In larger amounts, and various concentrations are prepared. When the temperature Is constant room be monitored. When the temperature is being varied a water bath will be used to heat up the acid and theosophical to the necessary temperature.
I decided which temperatures and concentrations to use during my preliminary series of experiments – 1 mol/dim of HCI (acid concentration will be fixed) 10-egg/dim of sodium theosophical (all of these concentrations will be tested in turn going up in steps of g/dim) 0-ICC temperature (all of these temperatures will be used going up in steps of 1 coo Concentrations of 5, and 40 g/dim of theosophical were available to me but my preliminary work showed that the 5 g/dim and egg/dim were too slow and fast respectively in reacting to be worth testing.
Similarly any temperature below ICC reacted too slowly, and ICC and ICC reacted too quickly to be worth including in my final results. Using my preliminary experiments I decided on using the following apparatus: 1 thermometer 1 beaker 2 measuring cylinders 1 conical flask 1 tripod 1 gauze 1 heatproof mat 1 stopwatch 1 Bunsen burner X board 1 pair of tongs 1 apron Method: – Experiment 1 – Changing the concentration 5 CM of HCI (at concentration 1 mol. dim) and 15 CM of sodium theosophical (at varying concentrations – 10 to 35 g/dim) are poured out into two measuring cylinders and then poured into a conical flask, which is placed on top of a board marked with letter X. The stopwatch will now be started. When the mixture has turned sufficiently cloudy so that the letter X can no longer be seen the stopwatch will be stopped and the time will be recorded. The experiment is repeated with all the concentrations. The whole procedure is then repeated. Experiment 2 – Changing the temperature 5 CM of HCI (at concentration 1 mol. dim) and 15 CM of sodium theosophical (at varying concentrations – 10 to 35 g/dim) are poured out into two measuring cylinders. A beaker is half filled with hot water from a tap. The water is placed on top of a Bunsen on a blue flame and the two measuring placed inside the water bath. The water is heated to the necessary temperature (ICC to ICC) then the two measuring cylinders are taken out and the contents of both are poured into a conical cylinder. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is the repeated.
Repeat results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help to iron out any anomalies and the average will give a good summary of the results of the experiment. However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results. Safety – A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. An apron will also be worn to protect the skin and clothing.
When handling hot beakers and measuring cylinders a pair of tongs will be used. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment. Fair Test – In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for Judging when the X has disappeared. I will make sure that the measuring cylinders for the HCI and theosophical will not be mixed up. The amount of HCI will be 5 CM each time, and the amount of theosophical will be fixed at 15 CM. During the heating stage of the experiment, a used to maintain continuity.
All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful. Prediction – I predict that as the temperature is increased the rate of reaction will increase. I also predict that as the concentration of the sodium theosophical increases the rate of reaction will increase. This means that both graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction ill not be exactly the same as the counterrevolutionaries is increased. This can be Justified by relating to the collision theory.
When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. All this can be understood better with full understanding of the collision theory itself: For a reaction to occur particles have to collide with each other.
Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or EAI. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the recent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.
Concentration – If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other. Pressure – If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction. Surface Area – If a solid is powdered then there is a greater surface area available for reaction, compared to the same mass of unprepared solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas.
The particles in a gas undergo random collisions in which energy is transferred between the colliding particles. As a result there will be particles with differing energies. Maxwell-Balletomane energy distribution curves show the distribution of the The main points to note about the curves are: 1 . There are no particles with zero energy. 2. The curve does not touch the x-axis at the higher end, because there will always be mom particles with very high energies. 3. The area under the curve is equal to the total number of particles in the system. 4.
The peak of the curve indicates the most probable energy. The activation energy for a given reaction can be marked on the distribution curve. Only particles with energy equal or greater than the activation energy can react when a collision occurs. Although Maxwell-Balletomane distribution curves are for the particles in a gas, the same distributions can be used for the particles in a liquid or solid. Effects of a temperature change – The graph below shows Maxwell-Balletomane striation graphs for a fixed mass of gas at two temperatures – TTL and TO, where TO is roughly ICC higher than TTL .
The total area under the curve remains the same, since there is no change in the number of particles present. A small increase in temperature causes significant changes to the distribution energies. At the higher temperature: 1. The peak is at a higher energy. 2. The peak is lower. 3. The peak is broader. 4. There is a large increase in the number of particles with higher energies. It is the final change that results increase in rate, even with a relatively small increase in temperature. A small increase in temperature greatly increases the number of particles with energy greater than the activation energy.
The shaded areas on the energy distribution curves show this. Effect of a catalyst – A catalyst works by providing an alternative reaction pathway that has lower activation energy. A catalyst does not alter the Maxwell-Balletomane distribution. Because a catalyst provides a reaction route of lower activation energy,