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Rate of Reaction Experiment - Sodium Thiosulphate and Hydrochloric Acid

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Rate of Reaction Experiment - Sodium Thiosulphate and Hydrochloric Acid

Plan

Aim: Our aim of this experiment is see the effect of Sodium
Thiosulphate and Hydrochloric Acid by testing different concentrations
and looking at how it affects the rate of reaction.

For my chemistry GCSE course work I am going to look at the factors
that affect the rate of reaction. It can be changed by 4 main factors:
Catalyst, Temperature, Surface area and Concentration.

To increase the rate of a reaction you need to increase the
number of successful collisions. The formula for this experiment is

How Catalysts effect the rate of reaction
==========================================

What is a catalyst?

A catalyst is a substance, which speeds up a reaction, but is
chemically unchanged at the end of the reaction. When the reaction has
finished, you would have exactly the same mass of catalyst as you had
at the beginning.

To increase the rate of a reaction you need to increase the number of
successful collisions. You can do this by providing an alternative way
for the reaction to happen which has a lower activation energy. Adding
a catalyst has exactly this effect on activation energy. A catalyst
provides an alternative route for the reaction. That alternative route
has lower activation energy. All this speeds up the reaction.

How the Temperature affects the rate of reaction

Increasing the temperature makes the reactant particles move faster so
they collide with each other more often causing quicker reactions.
They hit each other harder because they have more energy. Almost any
other reaction will happen quicker when heated. When the particles
collide harder and more often, this is increasing the collision
theory. The collision theory: when particles react they first have to
collide. If the particles collide with less energy than the activation
energy, nothing important happens. They bounce apart. Only those
collisions, which have energies equal to or greater than the
activation energy, can make reaction.

How the surface area affects the rate of reaction

If you increase the surface area then there is more space for the
reaction to take place. This will speed up the reaction because there
will be more space for a bigger reaction quicker.

How Concentration affects the rate of reaction

In a reaction where either one or both of the reactants are in a high
concentration the particles are closer together and will collide more
with one another more often. Therefore there will be an increase in
the number of successful collisions. This is increasing the rate of
reaction.

In our experiment we have chosen to change the concentration. We will
be using five different concentrations: 2 M, 1.5 M, 1 M, 0.5 M and
0.25 M.

Preliminary work

Prediction

I predict that the higher the concentration of acid the quicker the
experiment will be because of the particles are closer together and
will collide more with one another more often. Therefore there will be
an increase in the number of successful collisions. This is increasing
the rate of reaction.

Equipment list

1. Safety Goggles
2. Conical flask
3. Measuring cylinder (no more than 30cm)
4. 0.25, 0.5, 1, 1.5, 2 M Hydrochloric Acid
5. Sodium Thiosulphate
6. Stop Watch
7. Cross drawn on a piece of paper
8. Diluted Water

Method

1. Collect equipment.

2. Draw a cross on a piece of paper.

3. Measure 20cm of Sodium Thiosulphate and put it into a conical
flask.

4. Wash the measuring cylinder.

5. Add 20cm of Hydrochloric acid into the conical flask with the
sodium Thiosulphate.

6. Time how long it takes for the cross to disappear.

7. Do each concentration 3 times then add the totals up and divide by
three to get an average.

8. Test all 5 concentrations this way and make sure you wash the
measuring cylinder after test to avoid contamination.

The range of data collected was very similar, as all the results seem
to follow a trend, which was as I predicted and it made it a lot
easier. As my prediction said the higher the concentration the quicker
the reaction was. We did not have any anomalies results that were way
out; they were all good results to get a good average.

From our preliminary work I found out that that we had to be very
careful in between each test to make sure the same person was watching
the cross because when one person had thought it had gone the other
person thought they could still see it. If we were going to do this
experiment using the best things we could to get the most accurate
results we would use a light beam. Then we would be able to see the
light through the conical flask but when the reaction had occurred we
wouldn’t. This would be when the reaction had finished.

When testing we can only use up to 2 molar because anything above that
is very dangerous as it is very harmful to skin. We had to be very
careful and make sure it doesn’t make contact with us. We made sure we
wore our safety goggles because I the Hydrochloric acid got into your
eyes it would be very harmful and it would probably blind you. From
our results table we found out that the higher the concentration the
quicker the particles react causing a quicker rate of reaction.

Main Experiment

Prediction

Again I predict that the higher the concentration of acid the quicker
the experiment will be, due to the fact that the particles are closer
together and will collide more with one another more often. Therefore
there will be an increase in the number of successful collisions. This
is increasing the rate of reaction.

Method

1. Collect equipment.

2. Draw a cross on a piece of paper.

3. Measure 20cm of Sodium Thiosulphate and put it into a conical
flask.

4. Wash the measuring cylinder.

5. Add 20cm of Hydrochloric acid into the conical flask with the
sodium Thiosulphate.

6. Time how long it takes for the cross to disappear.

7. Do each concentration 3 times then add the totals up and divide by
three to get an average.

8. Test all 5 concentrations this way and make sure you wash the
measuring cylinder after test to avoid contamination.

GRAPH

From our results I can see that my readings were a lot higher than
last time this is not because I have done it wrong but the fact that
the technicians make the solutions and they wont produce the same
solution every time. From our results I can see that either the Acid
was weaker than our preliminary experiment or that our Sodium
Thiosulphate was a lot stronger. Even though we haven’t got the same
results that we had last time it still followed the pattern that the
higher the concentration the quicker the reaction.

Analysis

I have drawn a graph for my results. Instead of joining cross for
cross I drew a curve of best fit. This makes the graph professional,
as it doesn’t have any results that do not follow the pattern. If you
come across some results that do not follow the pattern a line of best
fit will still make the graph easy to read and it will follow a trend.

This graph is easy to read and it shows a strong correlation and shows
my results in a more accurate way than the table as you can see the
trend straight away. From our graph I have found out that there is a
strong correlation between the amounts of Hydrochloric acid to Sodium
Thiosulphate in terms of reacting quicker or slower. The trend in the
graph supports my prediction as you can see the M going up the x-axis
and the time (in seconds) going across the y-axis. As you can see from
our graph the trend is as I predicted it would be.

From looking at my results and graph I am able to conclude that the
more concentrated the acid the quicker the reaction happened and the
more gas was produced. Before I did the experiments I made some
predictions, they were that the more concentrated the acid was, the
quicker the reaction would happen. This was completely correct, what I
thought would happen did happen. From looking at my graph I can tell
that the graph is directly proportional to the data given off by this
experiment and my prediction, which was correct. At this point we are
able to answer our main hypothesis, which was “ how does the
concentration effect the rate of reaction”

Particle collision theory

The particle collision theory supports our results as you can see that
the higher the concentration of acid the more successful collisions
with the sodium thiosulphate causing it to react quicker, so this
graph does support the collision theory.

Increasing the concentration of acid molecules increases the frequency
or chance at which they hit each other (slower-faster).

Evaluation

My prediction of the concentration being directly proportional to the
rate of reaction is also correct.

From looking at my results and graph I am able to conclude that the
more concentrated the acid the quicker the reaction happened and the
more gas was produced. Before I did the experiments I made some
predictions, they were that the more concentrated the acid was, the
quicker the reaction would happen. This was completely correct, what I
thought would happen did happen. From looking at my graph I can tell
that the graph is directly proportional to the data given off by this
experiment and my prediction, which was correct. At this point we are
able to answer our main hypothesis, which was “ how does the
concentration effect the rate of reaction”

To make our experiment better we could do the test 5 times to get a
better average. We could use different measuring cylinders for every
test to give the most accurate result possible and it will avoid
contamination with water of the solution that has just been in the
measuring cylinder.

In doing our experiment there were a few problems. On some tests we
couldn’t tell if the cross had disappeared or not. This is all down to
human error and humans could never get the experiment perfect.

Even though we thoroughly washed the equipment in between each test,
there still could be a chance of contamination which would contribute
to less accurate results. We would need to use a different measuring
cylinder every time if we were to make it as accurate as possible. But
the school couldn’t provide over 30 measuring cylinders per group of
three or four.

We as humans have a slight delay so again human error causes the
results to be in accurate.

In the main experiment all our results were longer than the preliminary
results; this could be due to some of the problems stated above. To further
this investigation we could use a wider range of concentrations and test
each one more than three times to get a more accurate average.

The quality of our evidence is very good as it is what we predicted
using scientific knowledge that the higher the concentration of acid
the quicker the time takes to react.

Apart from one case when we didn’t know if the cross had gone and by
accident the person watching knocked the glass so we took 5 seconds of
the time, we did not have any anomalies (odd results) in any of our
results this was partly to do with the fact that we had experienced
our experiment before in the preliminary work. To further this
investigation we could use a wider range of concentration of acid or
different concentrations of sodium Sodium Thiosulphate. Also we could
change or verify the materials we used e.g. marble chips and
Hydrochloric acid. Instead of looking at the rate of reaction we could
look at how a catalyst, surface are or temperature affects the rate of
reaction using the same or different substances.

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"Rate of Reaction Experiment - Sodium Thiosulphate and Hydrochloric Acid." 123HelpMe.com. 24 Apr 2014
    <http://www.123HelpMe.com/view.asp?id=48251>.




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