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The Rate of Reaction Between Sodium Thiosulphate and Hydroch

作者:ihpa.net 发布时间:2017-09-28

In addition, every
person will start the clock at a different time; it could be when the
solution has been poured into the conical flask, or when the solution
is about leave the measuring cylinder. If you start the time at
different times, the experiment will be unfair and the results will be
inaccurate.

III.The same apparatus : - The same type apparatus must be used, as so
to increase the amount of accuracy. For example for measuring volumes,
if I use different measuring cylinder it will be an unfair test,
because different pieces of equipment has different degrees of
accuracy and because we can only measure to half an interval, the
amount we measure may be different, with different apparatus.

Also in some cases it is easier to pour solution in to some apparatus
then it is with others because is depends on how narrow the opening
is, for example solution would be harder to pour into a small conical
flask because the opening is a lot narrower than a larger flask.

In addition, it depends on how large the cross is on the paper, and
where it is placed. If the cross is changed and it is lighter then
obviously the time would decrease as it would be easier for the
reaction to cover. If the cross was placed on the bottom, the time
would be greater then if the cross was on the side because the
thickness that you would be seeing through is different and therefore
time different will be very different.

IV.Temperature : - Increasing the temperature always increases the
rate of reaction. In solution the particles are constantly moving. By
increasing the temperature the particles move faster because they have
more energy. They collide faster therefore the collision frequency
goes up.

Because more particles have more energy, a higher proportion will have
equal to higher than the activation energy, therefore the successful
collision frequency also increases. In addition, when a molecule
collides with another particle it transfers its energy to the other
particle, is this particle is hit constantly then it should obtain
more energy than then the activation energy and therefore reacting.

This is why a slight increase in temperature could affect the rate of
reaction. Therefore I must use the same temperature. I will be
conducting all of my experiments at room temperature, so there will
not be a significant difference in the temperature.

Hypothesis: -

Prediction: -

I predict that as the concentration of sodium thiosulphate increases
the rate of reaction will increase.

Explanation: -

This is because as the concentration increases more S2O32- ions will
come in contact with H+ ions, this because there will be more S2O3-2
ions. This can explained via collision theory. When two particles
collide they need a certain minimum energy called the activation
energy, if they have equal to or more than this energy, there will be
a successful collision. If the particles have less then this amount of
energy they will simply bounce apart. Therefore if the concentration
increases then more particles will come in contact, increasing the
collision frequency. Therefore, there will be more successful
collisions and there shall be an increase in the successful collision
frequency.

Justification of my predication: -

From this table I expect to find that as the concentration of sodium
thiosulphate goes up, the time of reaction will go down, and therefore
the rate of reaction will go up. The rate of reaction, is the number
of sulphur molecules created per second, but is equal to 1 divided by
the time; 1/time (s) or it can be written as time (s)-1.

From the graph, I hope to show that there is a trend between the two
key variables, which are time and concentration of sodium
thiosulphate. I hope that from the graph that my predication is
correct. I also want to prove that as the concentration of sodium
thiosulphate increases the rate of reaction increases.

In the time graph the line is curved and gradually decreasing. In the
rate graph, I predict that the graph is linear.

Preliminary Experiment: -

Apparatus:

1. 100ml and 250ml conical flask.

2. Two 50cm3 and one 10cm3 measuring cylinder.

3. Stop watch.

4. Sodium thiosulphate

5. Hydrochloric acid.

6. One sided stick label

7. Thick marker pen.

Method:

(a) Make sure the experiment is not close to the window or anything
that could change the temperature, because if the temperature changes,
the results could be affected.

(b) Wash all the apparatus out, so ensure that there is no
contamination, when the reagents are poured in.

(c) Take a one sided sticky label, and with a thick marker draw a
cross on the sticky side, then stick this label on the bottom of the
conical flask.

(d) Measure 5cm3 of sodium thiosulphate in the 10cm3 measuring
cylinder.

(e) Take the same measuring cylinder and fill up to the 30cm3 mark
with water. Then pour all of the contents into conical flask.

(f) Take 10cm3 measuring cylinder and measure 10cm3 of hydrochloric
acid.

(g) Pour this into the conical flask and immediately start the
stopwatch.

(h) When the cross is not visible when looking from above the conical
flask, then stop the timer and record the time on the table.

(i) Wash out the apparatus as not to cause any contamination for the
next time, so that there are chemicals left, which could affect
results.

(j) Repeat steps (a) - (f), but using 25cm3 of sodium thiosulphate,
then repeat steps (a) - (f) again, but using 30 cm3 of sodium
thiosulphate, these large amounts can be measures out in a 50 cm3
measuring cylinder.

(k) Repeat steps (a) - (g) using 5cm3 instead of 10cm3 of hydrochloric
acid. Then repeat steps (a) - (g) again using 15cm3 instead of 10cm3
of hydrochloric acid.

(l) Repeat steps (a) - (g), but change the concentration of
hydrochloric acid, and keep the concentration of sodium thiosulphate
constant.

Results

Experiment

Volume of Hydrochloric Acid

(cm3)

Volume of Sodium Thiosulphate

(cm3)

Volume of Water

(cm3)

Concentration of Sodium Thiosulphate

(M)

Time

(s)

Rate of Reaction

(s-1)

1

10

5

25

0.0833

135

0.0074

2

10

25

5

0.4167

22

0.0455

3

10

30

0

0.5000

18

0.0556

4

5

5

25

0.0833

173

0.0059

5

5

25

5

0.4167

30

0.0333

6

5

30

0

0.5000

22

0.0455

7

15

5

25

0.0833

125

0.0080

8

15

25

5

0.4167

20

0.0500

9

15

30

0

0.5000

17

0.0588

Experiment

Volume of Hydrochloric Acid

(cm3)

Volume of Sodium Thiosulphate

(cm3)

Volume of Water

(cm3)

Concentration of Hydrochloric Acid

(M)

Time

(s)

Rate of Reaction

(s-1)

10

5

20

10

0.1667

54

0.0185

11

10

20

5

0.3333

28

0.0357

12

15

20

0

0.5000

21

0.0476

Green - using 10cm3 of HCl.

Blue - using 5cm3 of HCl.

Red - using 15cm3 of HCl.

Yellow- varying the concentration of HCl, instead of Na2S2O3

[IMAGE][IMAGE][IMAGE]Graphs, when varying the concentration of Sodium
Thiosulphate

These graphs show that as the concentration increases the rate of
reaction increases.

[IMAGE][IMAGE]

[IMAGE]

These graphs, show that as the as the concentration increases there is
a gradual decrease in the time taken for the reaction.

Graphs, when varying the concentration of Hydrochloric acid

[IMAGE]

This graph shows that as the concentration increases there is a
gradual decrease in the time taken for the reaction. From this I can
determine that, if there is an increase in the concentration of
hydrochloric acid, then the time may be affect, as it will decrease
and be lower, therefore disturbing my results.

[IMAGE]

These graphs also show that as the concentration of hydrochloric acid
increases the rate of reaction increases, and because this is a
controlled variable, therefore a slight increase or decrease in the
concentration could have a large affect on the results.

Sources of Error

For the first experiment I used a small 100cm3 conical flask, this was
hard to pour into as the opening was narrower, therefore when pouring
the hydrochloric acid, I had to pour slowly, which may have effected
the results as I was timing, the experiment. Therefore for the rest of
the experiments I used a 250ml conical flask which was easier to pour
with. In the actual experiment I will use a 250ml conical flask, which
will be easier to pour into and I will be able to get more accurate
results.

I used three different volumes of HCl to see which one had more a
suitable range, so that the time was not too short or too long. I
shall use 10cm3 if hydrochloric acid because 5cm3 had a time which was
close to 3 minutes, while 10 and 15cm3 had their longest times closer
to 2 minutes. The results between 10cm3 and 15cm3 are not very
different, this is because we are only measuring the experiment until
the solution goes opaque, therefore there is an excess amount of HCl,
because we don't need an excess, I will use only 10cm3 in the
experiment.

The results could have been affected by the variable, temperature,
which can have a large affect even if this does not raise much. My
preliminary experiment has helped me to decide that I will try to keep
this constant. I will conduct all my experiments on one day, so that
the temperature will be closer together. In addition, I will keep the
experiment away from any doors, windows, flames or radiators which may
have may have an affect on the results.

Safety:

We will be using very low concentrations so there will be no hazards
with the chemicals. However, in case any glass is broken, immediately
clear up, and dispose of in the broken glass bin, not the ordinary.
Consult the teacher of any injuries or accidents.

Apparatus

1. 250ml conical flask.

2. Two 50cm3 and two 10cm3 measuring cylinder.

3. Stop watch.

4. Sodium thiosulphate

5. Hydrochloric acid.

6. One sided stick label

7. Thick marker pen.

Method

(a) Keep experiment away from anything which could change the
temperature of the experiment and affectively change the results.

(b) Wash out apparatus, as not to cause contamination.

(c) Take a one sided sticky label, and with a thick marker draw a
cross on the sticky side, then stick this label on the bottom of the
conical flask.

(d) Measure 5cm3 of sodium thiosulphate in the 10cm3 measuring
cylinder and pour into a 50cm3 measuring cylinder.

(e) Take the same measuring cylinder and fill up to the 30cm3 mark
with water. Then pour all of the contents into conical flask.

(f) Take another 10cm3 measuring cylinder and measure 10cm3 of
hydrochloric acid.

(g) Pour this into the 250ml conical flask and immediately start the
stopwatch.

(h) When the cross is not visible when looking from above the conical
flask, then stop the timer and record the time on the table.

(i) Wash the apparatus completely, as to not cause any contamination.

(j) Repeat steps (a) - (f), each time increasing the amount of sodium
thiosulphate by 5cm3 until 30cm3. Therefore, we have a range of 5, 10,
15, 20, 25 and 30cm3.

(k) Repeat steps (a) - (g) three time, so can have an average result
at the end, and the number of errors reduced and therefore we have
more accuracy, by dealing any anomalies.

How to control variables that could affect my results.

I will make the test fair, by controlling the person using the
stopwatch, which will be me; therefore my reaction time will stay the
same and therefore reducing errors. I will clean out the apparatus
each time, so that the apparatus is not contaminated, also I will use
the same apparatus. Temperature is very hard to control, I can not
make sure that it is exact, but the experiment will happen under room
temperature, which will be about 22 oC, and I will keep my experiment
away from anything, which could potentially heat up the experiment,
e.g. Bunsen flames and radiators. The concentration of HCl will be the
same, as we will not be making the concentration, but be provided with
it. The volume of hydrochloric acid, we can measure to the closest 0.5
cm3, there will be a little amount of error, but not much.

This is how I will record my results.

Experiment

Volume of Hydrochloric Acid

Volume of Sodium Thiosulphate

Volume of Water

Concentration of Sodium Thiosulphate

Time

Rate

(cm3)

(cm3)

(cm3)

(M)

(s)

(s-1)

1

10

5

25

0.0833

-

-

2

10

10

20

0.167

-

-

In addition, I will create a scatter graph for time against
concentration of sodium thiosulphate, and draw a best of best fit. I
will also draw a scatter graph of rate of reaction against sodium
thiosulphate, with a line of best fit.

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