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The rate of reaction between Sodium Thiosulphate and hydrochloric acid

Free essay example:

Chemistry investigation the rate of reaction between

Sodium Thiosulphate and hydrochloric acid

The question I am going to investigate is how the level of concentration would affect the rate of reaction.

I am going to do this by diluting sodium disulphate with hydrochloric acid and time it at every step. Because I would want to see how the concentration affects the rate of reaction.

Sodium Thiosulphate + Hydrochloric Acid → Sodium Chloride + Sulphur Dioxide + water + Sulphur

Na2S2O3+ 2HCl  2NaCl + SO2+ H2O + S

Equipment

Three different sized Beakers for hydrochloric acid, sodium Thiosulphate        

Two measuring cylinders to measure solutions

Twopipettesto obtain the correct volume of hydrochloric acid and sodium Thiosulphate

 A stop clock used to time the reaction.

One conical flask used as a reaction the container in which the reactants were addedtogether and the reaction allowed to progress

This equipment will help me more accurate, reliable results.

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The variable I have chosen to investigate are:

       • Input sodium thiosulphalte concentration        

       • Output reaction

I predict that the more the concentration the faster the chemical reaction.

The scientific reason for my predication is the more the concentration the quicker the reaction. Also if we increased the amount of Sodium Thiosulphate in the solution, the rate of reaction might increase. If there is a higher concentration of the Sodium Thiosulphate to react with the Hydrochloric acid, there will be a greater number of collisions, so leading to a faster reaction time.

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I will have to keep a number of factors under control and not change a few things. I will have to keep the temperature of the heat roughly the same. This is because different levels of heat would increase or decrease the reaction– if it is different for every test, then it would not be a fair test.

        I will need to make sure nobody shakes the beaker because that can move the solution and cause it to react faster. Doing this would make each test different because it will change the speed of reaction in each test and that will make the test unfair.

        The amount of Hydrochloric acid must always be kept the same because different levels will affect the rate of reaction. If it is higher or lower in any test, then the results of each test will be different. This will make the test invalid and unfair.

I believe that the following other factors may affect the results of my investigation and therefore I will need to control for them.

      1. Temperature

      2. Amount of concentration (Na2 s2 o3)

      3. The person taking the reading.

      4. The amount of acid.

      5. Keep the pipits the same.

The reason why I believe that each of those factors could affect my investigation is

  1. the temperature could effect the speed of reaction
  2. the more the concentration the faster the reaction
  3. the same person taking  the reading gives more accurate results
  4. if you change the acid its going to effects the rate of reaction
  5. changing the pipettes effects the experiment

The way I am going to control for each of these variables is

  1. make sure temperature is rate for the reaction
  2. make sure I have the amount of Na2 S2 O3
  3. The person taking the readers is the same
  4. the amount of acid does not change
  5. And that the pipits are kept m the right beakers.

6. Flask different concentration of sodium Thiosulphate placed in flask time take for solution to cloud and obscure x is recorded.

I will check that my technique gives my appropriate data by doing a preliminary experiment using the following amounts:

         Substance 1 Sodium Disulphate

         Substance 2 Hydrochloric Acid

  Substance 3 Water

The results of my first preliminary experiment was 50ML of Sodium Disulphate 5ML of Hydrochloric Acid = 33.06 second for the reaction to take place.

I will work out the range of values of my input variable by doing the following additional preliminary experiments:

          Preliminary experiment 2 = 30.94sec

          Preliminary experiment 3 = 32.31sec

          Preliminary experiment 4 (if needed)

          Range = biggest takeaway lowest

          Range = 33.06sec – 30.94sec = 2.12sec

From my preliminary work I have decided that the range of values of my input variable will be

          • From 12.5 cm3 concentration

          • To 100cm3 concentration

I will use the following values of my input variable

And will collect 3 values of each reading.

The way I am going to make sure that my results are accurate and reliable is repeating the experiment more than once.

I will use detailed scientific knowledge and understanding to make it more reliable and more effective results.

I will combine my values of each reading by working out the average of the values

I will use this method because is most accurate method.

My results table

Sodium Disulphate(ml)

Hydrochloric Acid(ml)

Water

%

T1(s)

T2(s)

T3(s)

50

5

0

100

33.06

30.94

32.31

40

5

10

80

44.12

49.28

47.72

30

5

20

60

62.72

64.92

67.82

20

5

30

40

107.65

115.94

86.78

10

5

40

20

267.75

195.06

251.22

5

5

45

10

578.78

578.78

578.78

0

5

50

0

963.28

967.02

967.94

My results table after I have processed the data using a mathematical relationship 1/time is the rate of reaction. To see how fast the reaction will go.

Sodium Disulphate(ml)

Hydrochloric Acid(ml)

Water

%

T1(s)

T2(s)

T3(s)

AV/T

Rate of reaction(seconde-1)

50

5

0

100

33.06

30.94

32.31

32.10

0.03

40

5

10

80

44.12

49.28

47.72

47.04

0.02

30

5

20

60

62.72

64.92

67.82

65.15

0.02

20

5

30

40

107.65

115.94

86.78

103.46

0.01

10

5

40

20

267.75

195.06

251.22

238.01

0.00

5

5

45

10

578.78

578.78

578.78

518.78

0.00

0

5

50

0

963.28

967.02

967.94

967.41

0.00

My evidence shows that the less the concentration the more the time.

I have chosen to draw graphs of

Graph 1 concentration against rate of reaction. I can do draw a line of best fit to see the positive correlation between rate of reaction and concentration.

Graph 2 concentrations against time. As the concentration increases the time taken decrease.

Relationship/Correlation

1 As my input variable gets bigger, my output variable tends to reduce.

2 As my inputs variable gets bigger, my calculated (second) output variable tends to decrease. This is because there is more collision between the amounts of particles.

My conclusion the more the concentration the faster the reaction. The scientific reasoning for this is the rate of reaction is affected by the concentration of solution used the more the concentration the faster the reaction.  Because larger number of collision increases the amount of bonds collision bonds form.

My conclusion supports my predication to the following extent.

That the more the concentration the faster the reaction because the solution was not at all dilutes in the first experiment. My predication was right.

The more you repeat the experiment the better it gets

If I completed my experiment again, I would improve it by:

Improvements to equipment more conical flask for all the experiment. There is less contamination

Improvements to techniques more hands to put the solutions in at the same time. It would improve the accuracy the time would have been started at right   time because there are more people doing it.

Improvement to how to collect the data.  I could have made it more reliable by using gas syringe to measure the rate of reaction. The problem with old method is that it allows lot of error.

I had the following anomalies around 20ml should have been between 107 and 117 but the actual result is 86 is faster. There was another anomalies 10 ml which should been around 267 and 251 but the actual result I got is 195.  These were potentially caused by not timing it properly and measuring it concentration badly. If we repeated more would of got better result. Another improvement I will do is controlling the temperature by using water bath.

 I believe my evidence is reliable because we repeated the experiment more than once.  Data was close and it seems more accurate.

I believe my evidence is sufficient to support my conclusion for the following reasons because my experiment was reliable.  My predication and scientific knowledge and the result more or less support each other it make my conclusion stronger.

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

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