Rate of Reaction Investigation

Rate of Reaction Investigation:

Introduction:

The rate of reaction measures how fast a chemical reaction occurs. You can change the rate of reaction in different ways such as changing the concentration of either the Sodium Thiosulphate Solution or the hydrochloric acid. Temperature can also be used to change the rate of reaction as the hotter the temperature is the faster the reaction occurs. I could also use a catalyst to provide a lower energy route for the reaction to occur. This would cause the speed of reaction to increase as it would increase the collisions. Although in this case I am not using a catalyst in my experiment so this means that I have controlled this key factor. In my experiment I am not using surface area as a facto but I do know that the small the particle the faster the reaction. This only applies when using solids in an experiment.

Preliminary Work: Results Table

These are the preliminary results. This was when we were experimenting and practising how to do the method. Whilst doing this we determined which dilution of STS and the acid worked the best and came up with reliable and accurate times. These below are the five best dilutions we came up with:

After choosing my best five solutions we started to time each dilution. We repeated the method three times with the same solutions. This made my results more reliable and I was able to attain an average time for each dilution.

Before doing my final experiment I tried different solutions to decide which one was the best to use and which was the most reliable every time by looking at the results for my final experiment. To start with I used large and small measuring tube to measure out the amount of both the hydrochloric acid and the Sodium Thiosulphate solution. Whilst pouring the acid and STS into the large and small measuring tube I didn’t spill any. I poured the acid and the STS into a conical flask, which is good because it doesn’t allow any liquids to spill out.

These below are the five different dilution ranges that I have tried along with the times taken:

The formula to work out the rate of reaction is = 1

Average time

I tried 5 different dilution ranges and I have come to a conclusion that the best one is:

It is the ...

This is a preview of the whole essay

These below are the five different dilution ranges that I have tried along with the times taken:

The formula to work out the rate of reaction is = 1

Average time

I tried 5 different dilution ranges and I have come to a conclusion that the best one is:

It is the best choice because the times are closer to each other unlike all of the other solutions. This means that I will always get consistent and reliable results.

Equations of my investigation:

Word Equation:

Sodium Thiosulphate + Hydrochloric Acid Sodium Chloride + Sulphur + Water + Sulphur Dioxide

Symbol Equation:

Na2S2O3 + 2HCl 2NaCl(aq.) + S(s) +H2O + SO2

Equipment Used:

Conical Flask I used this because when I shake the Thiosulphate and acid/water together it won’t spill out of the beaker and therefore I won’t get an inaccurate result.

Beaker: I have used this beaker to contain my Thiosulphate solution until it needs to be measured in the large measuring tube.

Stopwatch: I choose to use a stopwatch because it is accurate in taking times because it has a reading of two decimal places.

Paper with an ‘x’: I used this to determine whether the solution had gone cloudy enough, so when I couldn’t see it I knew when to stop the stopwatch.

Small measuring tube: I choose this instrument to measure out the hydrochloric acid before I was to be added to the bottleneck beaker for reaction.

Large measuring tube: this would be needed to contain the Sodium Thiosulphate solution. I choose a large tube because I need to add a lot of STS. I measured out the Thiosulphate solution before I added it to the conical flask. I also choose to use a different size beaker so it wouldn’t be mixed up with the acid/water and cause an unfair test. If this happened it would either cause the reaction to start prematurely or it would dilute the water before added to the bottleneck beaker.

Pen + Paper: I choose to choose these to record my results quicker rather then using a computer which takes a lot more time consuming. It’s a much quicker and easier method than recording my results into a computer.

Goggles: I had to use goggles to protect myself from the acid and STS.

How did I make it a fair test?

Throughout my experiment I used the same equipment every time I repeated my different solutions. I was also careful to measure out the correct amounts of Sodium Thiosulphate Solution, acid and water so I tried to get the same results as before. I was also careful not to use the same measuring tubes and beakers so that I wouldn’t get the solutions mixed up and therefore it could start the reaction prematurely. Also to make it a fair test I repeated my different solutions 3 times and took an average time for each of them.

Method:

I started by collecting all of the equipment:

Normal shaped beaker
Conical flask
Stopwatch
Paper and pen
Small measuring tube
Large measuring tube
Goggles

Then I began by collecting my Hydrochloric acid and Sodium Thiosulphate solution. I collected the acid in its actual bottle so when I won’t some acid I can just measure it out into my small measuring tube. I collected the Sodium Thiosulphate Solution in a normal measuring beaker.

We then measured out the sodium Thiosulphate solution into the large measuring tube e.g. 50ml. Then I measured out the acid into the small measuring beaker and also water if I needed to dilute it for one of my solutions.

After measuring out the STS, acid and water I would then pour them both into the bottleneck beaker, swirl it around to kick start the reaction, and then begin timing. Then we placed the bottleneck beaker over the piece of paper with the black cross on it. When we were unable to see the ‘X’ because the solution went cloudy (which was a sign of the reaction taking place) we stopped timing. We then recorded the time for the correct solution. Once we had done all of that we poured the solution down the sink and thoroughly rinsed out the beaker to keep it a fair test. For the next solution we repeated the same method but only changing the amount of acid, STS and water, and if needed the concentration of the solution as well.

After collecting all of my results we tidied out equipment away.

Safety:

For safety we simply wore goggles to protect our eyes from the acid and STS otherwise it can damage our eyes.

Evaluation

To make our results more reliable we could have used temperature to see how it would affect the results e.g. hotter the solution the faster the reaction time, by doing this we would have seen a trend in our results. We could have used the same dilutions but change the temperature to help show how the reactions can change due the environment as well as the dilutions. To see if our results change by using the same dilutions, we could have change the surface area, by making the surface area bigger the reaction time should be faster, this is because it causes the particles to collide more. Another way we could have changed the reaction time is by using a catalyst. Catalysts work by using an alternative mechanism involving a transition state and lower energy. This means that more collisions will take place which causes more energy to reach the transition state.

Throughout the experiment there was only one anomaly which was in the 4th dilution, the times were:

1) 112.63

2) 89.82

3) 103.08

The time highlighted was the anomaly in the 4th dilution, this is because it is so far of the other times and therefore it is not a reliable result. I have also noticed that the more dilute the solution, the slower the reaction. Because of the anomalies we should ignore these as they could change the average time and therefore the reliability of the result. Also because we repeated the experiment we should make sure that the concentration of the acid is the same as this could change the time of reaction.

This is because the errors bars are so small it shows that our results are reliable as there is less room for error. It is clear that the 3rd solution has a big error bar because the range of results is big. We chose the 2nd solution because the error bar is the smallest of them all which shows that it is the most reliable one of them all.

We could have changed the beakers every time we carried out another solution so it the measurements would be accurate. Also we could have repeated our solutions more. For example we did 3 repeats in this experiment so we could have done 5 or 10 to make the results more reliable and accurate results.

Peer Reviews

Here's what a star student thought of this essay

aranstar

14th of Feb 2012

Quality of writing

This coursework in terms of spelling, grammar and punctuation was great with the exception of a few sentences that needed altering. The student used technical terms; however I noticed that the student abbreviated the word Sodium Thiosulphate as STS on several occasions. This is not a good habit in chemistry, and as the coursework was typed out on the computer, it would have been better if the whole word Sodium Thiosulphate was written, if not, then the formula Na2S2O3 would have sufficed.

Level of analysis

I was disappointed to see that the student included no analysis whatsoever. The coursework was written more as an explanation and description rather than an analysis. As a student that has already partaken in many similar investigations, I have learnt that analysis is key, and although the student has included their final readings, there is no sign of a graph, neither any detailed breakdown of the results.

Response to question

The students response to the question, or rather investigation, was set out good, with necessary precautions taken into action and also explained the reasoning behind it. The student carried out preliminary tests before the actual test, making sure the results were as accurate as possible both times, which is excellent practice for any chemical experiment. Another great thing is the inclusion of suggestions and improvements of what could have been better. However, in all chemical experiments, it is also good practice to give a prediction and explain the reasoning and theory behind everything. This coursework includes none of that, and whilst every procedure of the experiment is described explicitly, one of the most important features has been missed out which could mean a difference of grade. The coursework includes two diagrams at the bottom that have no caption or explanation showing it is unfinished which is not a good way of submitting coursework.

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