The Effect Of Concentration On Rate Of Reaction Engineering Essay

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The colour of the sodium thiosulphate solution in the conical flask turns from colourless to yellowish milky when the hydrochloric acid is poured into the conical flask.

The X-sign on the paper disappear as the sodium thiosulphate solution reacts with hydrochloric acid in the conical flask.

During the reaction between sodium thiosulphate solution and hydrochloric acid, there are some smell produce due to the formation of the yellow substance in the conical flask.

QUANTITATIVE DATA

Experiment

Volume of sodium thiosulphate ( ml )

Volume of distilled water ( ml )

Volume of hydrochloric acid

( ml )

Time taken for the X-cross on white paper to disappear ( s )

1

2

3

1

80.0

0.0

10

15.08

14.66

14.79

2

70.0

10.0

17.28

16.23

17.85

3

60.0

20.0

19.70

21.37

20.48

4

50.0

30.0

23.69

26.34

24.88

5

40.0

40.0

28.86

29.84

31.90

6

25.0

55.0

52.85

48.54

49.57

7

15.0

65.0

96.80

94.35

95.88

8

10.0

70.0

152.57

138.19

145.09

Table shows the time taken for the reaction between sodium thiosulphate solution and hydrochloric acid with different concentration.

ASPECT 2 : PROCESSING RAW DATA

S2O32- ( aq ) + 2H+ ( aq ) H2O ( l ) + SO2 ( g ) + S ( s)

Average time taken and the reciprocal of time

Experiment

Time taken for the X-cross on white paper to disappear , t ( s )

1

2

3

Average

=

1

15.08

14.66

14.79

=

=14.84

2

17.28

16.23

17.85

=

=17.12

3

19.70

21.37

20.48

=

=20.52

4

23.69

26.34

24.88

=

=24.97

5

28.86

29.84

31.90

=

=30.20

6

52.85

48.54

49.57

=

=50.32

7

96.80

94.35

95.88

=

=95.68

8

152.57

138.19

145.09

=

=145.28

Table shows the average time taken and the reciprocal of time

Molarity of sodium thiosulphate solution

M1V1 = M2V2

Where , M1 = molarity of the sodium thiosulphate solution before dilution

V1 = volume of the sodium thiosulphate solution before dilution

M2 = molarity of the sodium thiosulphate solution after dilution

V2 = volume of the sodium thiosulphate solution after dilution

Example : For Experiment 1

M1V1 = M2V2

( 0.2 mol dm-3 ) ( = ( M2 ) ( )

M2 = 0.2 mol dm-3

Experiment

Volume of sodium thiosulphate solution before dilution ( ml )

Volume of distilled water ( ml )

Volume of sodium thiosulphate solution , water and hydrochloric acid after dilution ( ml )

Molarity of the sodium thiosulphate solution before dilution (moldm-3)

Molarity of the sodium thiosulphate solution after dilution (moldm-3)

1

80.0

0.0

80.0

0.2

0.2000

2

70.0

10.0

0.1750

3

60.0

20.0

0.1500

4

50.0

30.0

0.1250

5

40.0

40.0

0.1000

6

25.0

55.0

0.0625

7

15.0

65.0

0.0375

8

10.0

70.0

0.0250

Table shows the molarity of the sodium thiosulphate solution after dilution

Figure shows the graph of molarity of sodium thiosulphate solution after dilution against time

Figure shows the graph of molarity of thiosulphate solution against reciprocal of time

Uncertainty of molarity of diluted sodium thiosulphate

Where , = Uncertainty of molarity of sodium thiosulphate

= Molarity of sodium thiosulphate

= Uncertainty of molarity of diluted sodium thiosulphate

= Molarity of diluted sodium thiosulphate

= Uncertainty of volume of sodium thiosulphate

= Volume of sodium thiosulphate

= Uncertainty of volume of diluted sodium thiosulphate

= Volume of diluted sodium thiosulphate

Example : Experiment 1

=

=

= ±0.0025

= ±0.003

Experiment

Uncertainty of molarity of diluted sodium thiosulphate

1

± 0.003

2

± 0.002

3

± 0.002

4

± 0.002

5

± 0.002

6

± 0.002

7

± 0.001

8

± 0.001

Table shows the uncertainty of molarity of diluted sodium thiosulphate in each experiment

Uncertainty of the time taken for the X-cross on white paper to disappear

ΔT =

Where, ΔT = Uncertainty of time taken for the cross to disappear

T = Average time taken for the X-cross to disappear

T1 = First trial of time taken for the X-cross to disappear

T2 = Second trial of time taken for the X-cross to disappear

T3 = Third trial of time taken for the cross to disappear

n = Number of trials

Example : Experiment 1

ΔT =

=

= ± 0.005

= ± 0.01

Experiment

Uncertainty of the time taken for the X-cross on white paper to disappear

1

± 0.01

2

± 0.00

3

± 0.01

4

± 0.00

5

± 0.00

6

± 0.00

7

± 0.01

8

± 0.01

Table shows the uncertainty of the time taken for the X-cross on white paper to disappear

Percentage uncertainty =

Absolute uncertainty =

Measurement and apparatus

Experiment

Trial

Reading (OC)

Percentage uncertainty (%)

Total percentage uncertainty

Absolute uncertainty

Time taken for the reaction between sodium thiosulphate and hydrochloric acid in the experiment of the effect of concentration on the rate of reaction by using stopwatch (±0.01 s )

1

T1

15.08

=

=0.0663

0.0663 % + 0.0682 % + 0.0676 %

= 0.2021

=

= 0.03

T2

14.66

=

= 0.0682

T3

14.79

=

= 0.0676

Table shows the example of calculation for absolute uncertainty based on experiment 1 for the reaction between sodium thiosulphate and hydrochloric acid

Measurement and apparatus

Experiment

Total perentage uncertainty

Absolute uncertainty

Time taken for the reaction between sodium thiosulphate and hydrochloric acid in the experiment of the effect of concentration on the rate of reaction by using stopwatch (±0.01 s )

1

0.0663 % + 0.0682 % + 0.0676 %

= 0.2021

=

= 0.03

2

0.0579 % + 0.0616 % + 0.0560 %

=0.1755

=

= 0.03

3

0.0508 % + 0.0468 % + 0.0488 %

=0.1464

=

=0.03

4

0.0422 % + 0.0380 % + 0.0402 %

=0.1204

=

=0.03

5

0.0347 % + 0.0335 % + 0.0313 %

=0.0995

=

=0.03

6

0.0189 % + 0.0206 % + 0.0202 %

=0.0597

=

=0.03

7

0.0103 % + 0.0106 % + 0.0104 %

=0.0313

=

=0.03

8

0.00655 % + 0.00724 % + 0.00689 %

=0.02068

=

=0.03

Table shows the percentage uncertainty, total percentage uncertainty and absolute uncertainty

Uncertainty of the rate of reaction

= +

Where, ΔR1 - Uncertainty of the rate of reaction

R1 - Rate of reaction

ΔM2 - Uncertainty of molarity of diluted sodium thiosulphate

M2 - Molarity of diluted sodium thiosulphate

Δt - Uncertainty of the stopwatch

T - Average time taken for the X-cross on white paper to disappear

Example : Experiment 1

=

= 0.06739

= ± 0.001

Experiment

Uncertainty of rate of reaction

1

± 0.0010

2

± 0.0007

3

± 0.0007

4

± 0.0007

5

± 0.0007

6

± 0.0006

7

± 0.0003

8

± 0.0003

Table shows the uncertainty of rate of reaction for each experiment

Degree of precision : coefficient of variation

Average measurement =

Standard deviation =

Coeffiecient of variation =

Experiment

Average time taken ( s )

Standard deviation

Coefficient of variation

1

14.84

=

=0.1756

=

=1.183

2

17.12

=

=0.6710

=

=3.919

3

20.52

=

=0.6823

=

=3.325

4

24.97

=

=1.084

=

=4.341

5

30.20

=

=1.267

=

=4.195

6

50.32

=

= 1.838

=

=3.653

7

95.68

=

=1.010

=

=1.056

8

145.28

=

=5.872

=

=4.042

Table shows the standard deviation and coeffiecient of variation of each experiment

The reading is of the time taken for the reaction between sodium thiosulphate and hydrochloric acid is not precise as all the coefficient of variation for eight experiment is more than 1.

ASPECT 3 : PRESENTING RAW DATA

ASPECT 1 : CONCLUSION

Rate of reaction can be defined as a measure of the speed which products are formed, measured as the change in concentration divided by the change in time (Chang, 2010). There are four factors affecting the rate of reaction which are temperature, catalyst, total surface area and concentration (molarity). Generally, rate of reaction can be determined by using the formula :

Collision theory refers to the theory that assume that for reaction to occur, reactant molecules must collides with an energy greater than some minimum value and with proper orientation. There are three main ideas in collision theory which are the molecules must collide to react. Next, the molecules posses a certain minimum kinetic energy known as activation energy to initiate the chemical reaction and lastly, the molecules must collide in the right orientation. Hence, the effective collision occur when the reactant collide with an energy at least equal to the activation energy (Abdullah, Mohd Ismail, & Abu Bakar, 2003).

In this experiment, the aim of the experiment is to determine the effect of concentration on the rate of reaction. Hence, the reaction occur between sodium thiosulphate solution and hydrochloric acid. The chemical equation for the reaction is :

S2O32- ( aq ) + 2H+ ( aq ) H2O ( l ) + SO2 ( g ) + S ( s)

Therefore, the rate of reaction can be calculated by measured the time taken for a fixed amount of sulphur to be produced as the product of the reaction which in this experiment to indicate the formation of sulphur, there are X-cross was drawn on a piece of white paper and placed at the bottom of the conical flask. As the time passes by, when there are formation of sulphur, the X-cross will disappear by looking it through the mixture of sodium thiosulphate and hydrochloric acid in the conical flask. The rate of reaction of this experiment for the reaction between sodium thiosulphate and hydrochloric acid can be determined by using the formula :

Based on the results of the experiment , two graph were obtained which are the graph of the molarity of the sodium thiosulphate against time and the graph of molarity of the sodium thiosulphate against the rate of reaction.

Thus, based on the graph of the molarity of the sodium thiosulphate against time, the molarity of the sodium thiosulphate is inversely proportional to the time taken for the X-cross on the white paper to disappear. This is due to the decreasing in the molarity of the sodium thiosulphate solution that makes the time taken for the X-cross on white paper to disappear increases. When the molarity of sodium thiosulphate is high, the time taken for the X-cross on white paper to disappear will be faster. Meanwhile, when the molarity of sodium thiosulphate is low, the time taken for the X-cross on white paper to disappear will be slower.

Besides, based on the graph of the molarity of the sodium thiosulphate against rate of reaction, the molarity of the sodium thiosulphate is increase linearly to the rate of reaction. This is due to the increasing in the molarity of the sodium thiosulphate solution that makes the rate of reaction increases. When the molarity of sodium thiosulphate is high, the rate of reaction also increases. Meanwhile, when the molarity of sodium thiosulphate is low, the rate of reaction decreases.

In conclusion, the experiment shows that the molarity of the sodium thiosulphate gives effect to the rate of reaction as the molarity is one of the factor that affecting the rate of reaction. Therefore, when the molarity of the sodium thiosulphate increases, the number of particles of thiosulphate also increases. Hence, the frequency of collision increases and the number of effective collision also increases. Thus, the rate of reaction increases.

ASPECT 2 & 3 : EVALUATING PROCEDURE(S) & IMPROVING THE INVESTIGATION

WEAKNESSES

WAYS TO IMPROVE

Parallax error occur during the reading of the temperature by using thermometer and the volume of hydrochloric acid and sodium thiosulphate solution, distilled water and hydrochloric acid by using measuring cylinder

The position of the eyes should be perpendicular to the scale of the measuring apparatus to avoid parallax error.

The apparatus is not cleaned first before use them for the experiment.

The apparatus should be cleaned first to avoid impurities and errors in the reading.

The time taken for the experiment is not the same as the time taken recorded as there are delayed in time when the observer clearly see the X-cross is already disappear and the time keeper stop the stopwatch.

the stopwatch should be handle by the observer the time taken for the X-cross on the white paper disappear can be record immediately when the mixture turns cloudy and the X-cross had disappear

Table shows the weaknesses and ways to improve in the experiment of Hess's Law

LIMITATIONS

WAYS TO IMPROVE

The observer of the experiment did not realize the exact time when the mixture turns cloudy until the X-cross on the white paper disappear while swirling the mixture of the hydrochloric acid and sodium thiosulphate solution

The observer should be more careful and cautious by looking continuously through the mixture of sodium thiosulphate and hydrochloric acid in the conical flask to the X-cross on white paper that are place at the bottom of the conical flask.

Table shows the limitations and ways to improve in the experiment of Hess's Law

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