same time as the acid was poured onto the magnesium, to measure the start of the reaction to the finish of the reaction where the equivalent care was taken to stop the clock at the point the magnesium disappeared which was at the end of the reaction. While we set up the apparatus we kept the reactants separate so that the starting time of the reactants could be measured accurately and for it to be a fair test. We wore safety goggles when we did the experiment, to protect our eyes from the very harmful acid. We considered the factors in the reaction, and decided how we were going to control them.We kept our eyes on the experiment so that we could see exactly when we sholud´ve started the stop clock and stopped the clock. This way the rate of reaction(the time taken for the magnesium to disappear) was measured accurately for a fair test. We made sure the amount of magnesium used stayed the same in all the experiments(2cm long).
RESULTS
The results for, the time taken for magnesium to disappear when it is placed in different
Concentrations of acid are summarised below.
EXPERIMENT 1
From the results in the table and the graph we can see a steady increase in the rate of reaction as the concentration of the acid decreaes. This complies with my prediction.The graph shows that there is an increase in the rate of reaction as the concentration increases because the graph has it´s largest gradient or it is steepest at this point.When the graph was made into 1/time the result should have been a sraight line graph but it did not turn out this way even though concentration~1/time. This 1/time graph could be wrong because of inaccurate results so there seems to be no relationship between the concentration graph and the 1/time graph. We can see from the rate of reaction graph that when the concentration roughly doubles from (1.8 moles to 3 moles) the rate of the reaction doubles (from 60 to 25 seconds). Also we can see that as the reaction continues the concentration of the reactants decrease and so does the rate of the reaction as we can see the decreasing gradient on the graph steadily falling and coming to a stop when the reaction is complete and the magnesium has completely disappeared.
CONCLUSION
I can conclude that if you double the concentration of the acid the reaction rate would also double, this is because the ions are closer together in a concentrated solution. The closer together they are, the more often the ions collide. The more often they collide, the higher the chance of a reaction between the magnesium and the hydrochloric acid. Also because there are more particles in the solution which would increase the likelihood that they would hit the magnesium so the reaction rate would increase. The graph gives us a good device to prove that if you double the concentration the rate of reaction doubles. If you increase the number of particles in the solution it is more likely that they will collide more often. In the reaction, when the magnesium hit the acid, it fizzed and produced many bubbles it was silver in colour (which is one magnesium's physical properties silvery white metallic element), the activation energy of a particle gets higher with heat, the particles which have to have the activation energy are those particles which are moving, in the case of magnesium and hydrochloric acid, it is the hydrochloric acid particles which have to have the activation energy because they are the ones that are moving and bombarding the magnesium particles to produce magnesium chloride. The graph for 1/time had the form of an s curve and it did have some relationship with the other graph.
EVALUATION
There are many reasons why our results for the 1/time graph did not prove the point that
concentration~1/time,such as
1)When the reaction takes place bubbles of H2 are given off ,which might stay around the Magnesium which therefore reduces the surface area of the magnesium and so the acid Cannot react properly so this affects the results.
2) We could have controlled factors in the investigation better (e.g the stirring of the Solution because if this isn't done properly it can lead to incorrect results).
3) Using larger concentrations of acid would give a bigger more accurate conclusion Instead of just using 10ml testubes use 1litre testubes, this way graphs would be more Spaced out and give an accurate form or curve
* Hypothesis
I predict that as the surface area increases, the speed of the reaction will increase therefore the gas will be produced faster. I believe this because most chemical reactions happen faster when there is more of the reactant to react with.When there is a larger surface area, there is more of the reactant available which makes it easier for them to react together. Usually, when the surface area is doubled it will double the rate of reaction.
Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the surface area is increased the particles have a bigger surface to react with so more molecules can react at a time. This means that they are colliding more often and there is a bigger chance that the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.
* Variables to be changed
Surface Area
This is the only variable to be changed to make this a fair experiment. I will change this to 1cm by 6mm, 2cm by 3mm, 3cm by 2mm, 4cm by 2mm, 5cm by 2mm, 6cm by 1mm.
*Variables to be kept constant
Temperature
The temperature will be kept constant at room temperature.
The amount of acid
The amount of acid will be kept constant at 100ml.
The concentration of the acid
The concentration of the acid will be kept constant at 2mol/dm3
The amount of Magnesium ribbon
The amount of magnesium ribbon will be kept constant at 6cm by 1mm.
* Pilot Experiment
To decide on the best mass of magnesium a number of calculations were done and a pilot experiment conducted.
The equation for the reaction is:
Magnesium(s) + Hydrochloric Acid(l) --> Magnesium Chloride(l) + Hydrogen(g)
Mg(s) + 2HCL(l) --> MgCl2(l) + H2(g)
We were advised to use roughly 0.05g of magnesium ribbon (found to be 6 cm long). The Relative Molecular Mass (RMM) of magnesium is 24, therefore the moles of magnesium to be used was:
Moles= 0.05
24
Moles= 0.0020833
It was decided to use an excess of hydrochloric acid to ensure all the magnesium reacted, therefore 100ml of acid was used in the pilot experiment. At room temperature 100ml of hydrochloric acid was added to 0.05g of magnesium and the gas was collected (see fig 1). The volume of gas produced was measured every 5 seconds. .
* Investigation Experiment
I am going to investigate how surface area affects the rate of reaction between magnesium and hydrochloric acid. The procedure for the experiment is as follows;
* Using a measuring cylinder, measure 100ml of 2mol/dm3 Hydrochloric Acid (HCL) an pour it into a conical flask.
* Measure 6 cm of magnesium ribbon and check on the balance that it weighs roughly 0.05g.
*Using a hammer to make sure there are no other ways the HCL can get onto the ribbon, bend the ribbon into a line of the desired length.
*Drop it into the conical flask and quickly put a bung on the conical flask (this must be done quickly to prevent gas escaping).
* Every 5 seconds measure the volume of gas produced until less than 1cm3 of gas is produced every 5 seconds.
* Repeat experiment two more times (for accuracy) and record all results in a table.
* Repeat the experiment for surface areas of 1cm, 2cm, 3cm, 4cm, 5cm and 6cm It is important that only the surface area is changed since this is what is being investigated.
Method
* Apparatus
I have chosen to use a 1000ml measuring cylinder to measure the volumes of substances used since it is more accurate than a pipette. A 100cm3 gas syringe should be appropriately accurate for measuring the gas produced since it is accurate to 1cm3 of gas. I will use a ruler to make sure exactly 6cm of ribbon is used each time.
* Variables
I have chosen to repeat the experiment 3 times because it therefore allows me to calculate an average rate of reaction. This will ensure that there are no anomalous results and it will increase accuracy. I have decided to start readings at 1cm and increase by 1cm each time until 6cm is reached, since it will allow me to see the increase in rate of reaction and 6 results should be enough to identify any trends.
* Rates of Reaction
Increasing the surface area increases the chance of the particles hitting the reactant and allows more particles to react with the reactant at once. The bigger the surface area of the magnesium, the greater the number of collisions, and therefore the rate of the reaction increase. Doubling rise in temperature almost doubles the rate of most reactions.
Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.
The evidence obtained shows us that Surface area is a large factor in determining the rate of reaction. This statement is backed up by the results graph.
Aim:
The aim of this investigation is to find out and observe how temperature affects the rate of reaction. I am going to investigate the changes caused to the solution of hydrochloric acid and sodium thiosulphate when the temperature is changed.
Prior Knowledge/Research:
The rate of reaction is the speed or velocity at which a chemical reaction precedes, expressed in terms of the amount of product formed or the amount of unit´s time taken for a certain reaction to occur (usually in seconds). Thus for the reaction of two compounds (in this case X and Y) that form a product (Z) the equation would be:
X+Y=Z
The Rate of Reaction varies greatly. Some chemical reactions, such as explosions, happen very quickly while others like rusting, occur very slowly. The rate of reaction can be affected by a number of factors: temperature, concentration and pressure, adding a catalyst, surface area/particle size and light. The one that I am going to be investigating and explaining about is Temperature.
Changes in temperature change the kinetic energy of the particles and hence the numbers of successful collisions with enough energy to break existing bonds and make product parties. The minimum energy needed for a successful collision is called the activation energy.
For a reaction to take place reagent molecules must collide with each other. When they do so, they must possess enough energy to cause or initiate a reaction. The level of energy needed to start a reaction is called its energy barrier. The actual energy needed to start a reaction is the activation energy e.g. a splint is needed to start a Bunsen burner in the process of combustion.
So in order to break the energy barrier, there has to be enough activation energy so the reaction will take place. Temperature helps to do this as increasing the temperature of the system increases the range of kinetic energies, increases the average kinetic energy and increases the population of particles with more than the activation energy essaybank.co.uk
Reaction mixtures contain particles that have different amounts of energy. Some particles are of very high energy whilst others are of relatively low or medium energy. A graph can be produced to show these variations in energy and it is known as an energy distribution curve:
The distribution curve shows that most of the particles have energy values close to that of the average energy value. The EA is the activation energy and the shaded area shows indicates the number of particles that have an energy amount that is equal to or greater than the activation energy. It is only these particles that can make the reaction occur taking into account that the activation is the minimum amount of energy needed for a reaction to occur. The shaded red area shows the total number of particles that have enough combined energy to react when they collide.
If the temperature is increased, the average temperature of the particles is increased so the graph shifts to the right as shown in graph 2. Now the total number of particles with energy equal to or greater than the activation energy has increased considerably.
The two theories that affect temperature and the rate of reaction are the kinetic theory and the collision theory. The kinetic theory clearly states that the positioning and movement of particles in a substance increases if the temperature increases. Therefore, increasing the temperature increases the energy between the particles and makes them move around a lot more and collide more often with each particle colliding with enough energy to get it past the energy barrier. If this is done successfully, then the collisions should have no problem passing the requirement stated in the collision theory that are: To react particles must collide with enough energy to break existing bonds and with the correct orientation to bring reactive sites close together. wwde dew esdedes ayde deba nde kcde deuk;
Bringing the reactive sites closer together means that the likelihood of a reaction occurring is increased so in a final research conclusion, increasing the temperature increases the rate of reaction speed.
Prediction:
As I explained earlier, the rate of a chemical reaction is the speed at which it takes place. Temperature is a major factor in this as increasing or decreasing the temperature changes the movement of particles in a substance therefore changing the rate of reaction. When a reaction mixture is heated up, each particle in it acquires more energy and collides more with other particles. wwdc dcw esdcdcs aydc dcba ndc kcdc dcuk.
Thus, from my prior knowledge and research, I can make the prediction that if you increase the temperature of a particular reaction, you increase the speed at which it takes place. This is simply because the particles carry more energy and collide more often where these collisions contain enough energy to break the energy barrier:
Temperature Raised Particles, when moving faster, collide with greater power. The reaction therefore becomes faster Collisions between particles are useless unless they break the energy barrier and this is exactly what increasing the temperature will allow them to do.
Apparatus:
The equipment I need to carry out the work and to obtain my results is:
· Sodium thiosulphate solution
· Hydrochloric acid
· 250cm conical flask
· -5 C -110 C thermometer
· 10cm /50cm measuring cylinder
· Heat proof mat
· Bunsen burner
· Wire gauze
· Tripod
· Stop clock
· White tile
· Filter paper
· A pair of Tongs
Diagram:
Preliminary Work:
Preliminary work is the work that is done beforehand for you to know that the values of chemicals and temperatures etc are all within a usable range and are pretty much guaranteed to work. It is a way for the person carrying out the experiment to know that it has been set up correctly for when the actual experiment begins.
For my preliminary work, I did the experiment but did not repeat it four times as I only wanted to see that the values that I was to be using were accurate. This preliminary work helped me to plan my actual investigation better as I learnt from my mistakes. These were things like not starting the stop clock, quick enough, which changed the times of my results, and using a little too much hydrochloric acid (10cm when I should have used 5cm ) that again made my results inaccurate.
Therefore, in the actual experiment I am going to be very careful when measuring the chemicals to get them accurate and starting the stop clock at the exact time the hydrochloric acid is added to again ensure fair and precise results.
Safety Precautions:
Throughout this experiment, I made sure that safety was one of my top priorities. I wore goggles at all times to protect my eyes; I wore a lab coat to prevent getting any chemicals on my clothing or me and used hazard cards. These told me the dangerous capabilities of chemicals that were to be using and what safety measures were needed when using these chemicals. I used a heatproof mat and tripod when using the Bunsen burner and took extreme caution when turning it on and off. I took the same extreme caution when I repeated the results, which I will talk about later on.
Method:
Firstly, I measured 50cm sodium thiosulphate solution using the conical flask. The appropriate temperature was checked using the thermometer. It was at this point where I carried out the various temperatures.
At the appropriate temperature, 5cm hydrochloric acid was measured using the measuring cylinders and then added to the flask containing the sodium thiosulphate. I now placed the flask over the paper, which had a black cross on it that I had drawn earlier.
The stop clock was started immediately to make results more accurate and the time in seconds for the cross to disappear was recorded in a table like the one below. I carried this out from room temperature (R.T) to 80 C. I used the Bunsen burner at each temperature with the heatproof mat on it and the wire gauze.
I repeated each temperature a total of 4 times to make my results accurate and calculated an average by which I compared each temperature with greater ease.
Observation
All rate of reaction experiment have visible results and this experiment is no exception. When I added the hydrochloric acid to the flask I observed immediately at each temperature to see the changes or reactions that were taking place between the particles.
When observing the experiment, the changes I saw take place were the tone of the sodium thiosulphate/hydrochloric acid solution. At the initial temperatures, which were quite low, the solution became very foggy and misty but only after a fairly long time. At the higher temperatures, the solution became fogy very quickly and in both cases, the solution continued to get foggy until it was no longer clear or transparent. I could not see through the solution at all. The colour of the solution went from a clear colourless liquid to a yellowish-green colour and at the higher temperatures, the colour changed almost immediately. I did not see any gas given off or any vigorousness in the actual reaction. The change in colour was smooth and there was no sound made when it happened. wwba baw esbabas ayba baba nba kcba bauk!
Fair Test:
To make my experiment a fair one, I had to look at a lot of things. Firstly, I looked at the factors that may have affected how well the investigation would work and these were things like using different equipment or doing the actual experiment in different conditions i.e. a colder/hotter environment. To combat this, I made sure that upon repeating the experiment, I used the exact same equipment and done it in the exact same environment to make absolutely sure that the experiment was fair at each temperature. wwgf gfw esgfgfs aygf gfba ngf kcgf gfuk;
I think that these were both very important factors because they could affect the results severely and leave me with an anomalous when I should only have correlating results. To ensure fair and accurate results, all of the factors that can affect my results need to be controlled.
Reliable Results:
To make my results reliable, I am going to be doing each temperature 4 times between the ranges of Room Temperature to 80 C. That´s nine different results altogether for the temperatures and the average that I will make from the four primary results that I record.
I will also make sure that each temperature is calculated to as accurate it can be as recording a result past the required temperature can mean unreliable results which makes the entire investigation void as one result is not calculated correctly.
Results:
I have decided to record my results in a table with a graph that is on a separate piece of graph paper:
Temperature( C) Time For Cross To Disappear Average
1 2 3 4
R.T 32.46 30.92 33.31 32.51 32.3
30 18.71 19.64 21.03 20.85 20.058
40 15.32 17 14.31 15.62 15.563
50 6.05 8.02 5.99 6.13 6.5475
60 4.07 3.78 3.65 2.87 3.5925
70 2.19 2.25 3.03 2.12 2.3975
80 1.53 1.24 1.41 1.66 1.46
Analysis Of Results:
From my results, I notice that there is a considerable difference in the time for the cross to disappear from the lower temperatures to the higher temperatures. All of the times are pretty much the same for the four different recording indicating that the experiment was a pretty successful one. There is no anomalousness and the average temperatures seem to descend, as the temperature gets higher. There is a decrease of almost 30 seconds from the starting temperature to the finishing one. from www.essaybank.co.uk
The table clearly shows that the time for the cross to disappear decreases as the temperature increases.
The reaction between Hydrochloric acid and Sodium Thiosulphate
When dilute hydrochloric acid is added to sodium thiosulphate solution, a fine deposit of sulphur is formed. The sulphur makes the solution cloudy. As more and more sulphur is formed, the solution becomes more and more cloudy. Soon it becomes impossible to see through the solution. The balanced equation for this reaction can be seen below.
Sodium + Hydrochloric Sodium + Water + Sulphur + Sulphur
Thiosulphate Acid Chloride Dioxide wweb ebw esebebs ayeb ebba neb kceb ebuk.
Na2 S2 O3 (aq) + 2HCL(aq) 2NaCL(aq) + H2O(l) + SO2 (g) + S(s)
Conclusion
From my results, I have come to the conclusion that if the temperature of a solution is raised, so is the time for the reaction to occur. The cross disappeared more rapidly as the temperature rose and I think this was due to the increase of energy between the particles and an increase in energy between collisions that successfully passed the energy barrier. This released the sulphur quicker and in larger doses, which turned the solution cloudy thus making the cross invisible. wwfd fdw esfdfds ayfd fdba nfd kcfd fduk.
At the lower temperatures, the time for the cross to disappear was less because the particles did not have as much energy as they did at the higher temperatures. At these temperatures the particles are colliding with much more energy and thus the reaction that releases sulphur works and now releases more sulphur at a much quicker rate thus increasing the rate at which the cross disappears. wweb ebw esebebs ayeb ebba neb kceb ebuk.
Heat From Room Temp. HEAT
Linking Prediction To Conclusion
My original prediction was that if you increase the temperature of a reaction, you decrease the time it takes to occur. And, from looking back on my results, I can see that this hypothesis was correct as the time for the cross to disappear decreased as the temperature rose. My conclusion matches my prediction very well overall, and my results clearly show this where at room temperature, the time for the cross to disappear was 32.3 seconds and at 80 C the time for the cross to disappear was 1.46- a difference of about 31 seconds. The particles were moving around with more energy; enough to break the energy barrier and for a reaction to occur as the temperature rose.
Evaluation
I think that this experiment has gone very well for me. My results were of a particularly accurate standard as I did each temperature the reaction was taking place four times and calculated an average from these times. There were no strange results (anomalies) within my results table and I think that this was because of the extreme caution and care that I put into making sure that the experiment was set up correctly with careful measuring of chemicals and substances.
I think that I could have repeated my results more however for the reason that I feel although the experiment was repeated four times, the most accurate results in experiment can only come from constant repeatability which I did not display in my experiment. That said, the time allocated did not allow me to do so and I believe as an improvement of what I could do if I did the experiment again, I would have to say that, with more time, I would repeat the results further for even more accurate and reliable results. dRotPBbVv from dRotPBbVv essay dRotPBbVv bank dRotPBbVv co dRotPBbVv uk
I believe that I could have improved the method by making it more specific. I stated clearly all the various methods I took in setting the experiment up but I could have been more specific to how all the apparatus was used and perhaps why I used the apparatus I did as well.
I believe that I did get a suitable range of results for this experiment. I recorded results from temperatures that ranged from Room Temperature to 80 C and I think that this is a very good range to see how temperature affects the rate of reaction. However, I feel that this also reduces the chance of knowing if anything changes if the temperature reaches a certain point. Perhaps doing the temperature even higher would enhance my results but this is also quite dangerous so I cannot really say that I could have improved the range of my results. wwdb dbw esdbdbs aydb dbba ndb kcdb dbuk.
Some other areas in the experiment that I feel I could have improved on were factors like controlling the stopwatch and measuring the amount of sodium thiosulphate and hydrochloric acid. There is lots of room for human error here. However the inaccuracies due to them were negligible because I paid close attention to these during the experiment.
Overall, this investigation has been a very successful one. I feel my results and analysis have been as accurate and reliable as they could have been under the time allocated. However I feel with extra time, I could have repeated the experiment and made it even more accurate and adapted it to try other variables i.e. concentration or adding a catalyst. These are the ways that I could expand on the original question.