Sunday 19 January 2014

PEKA Chemistry form 5 chapter 1 (To study the effect of the concentration of sodium thiosulphate, Na2S2O3, solution on the rate of reaction.)

Aim                             : To study the effect of the concentration of sodium thiosulphate, Na2S2O3,                                        solution on the rate of reaction.

Problem statement      : How does the concentration of sodium thiosulphate, Na2S2O3, solution affect the rate of reaction?

Hypothesis                  : The rate of reaction will increase if the concentration of sodium thiosulphate, Na2S2O3, solution increases.
When the concentration of sodium thiosulphate, Na2S2O3, solution increases, the rate of reaction increase.

Variables                     :-
Manipulated variable  : Concentration of sodium thiosulphate, Na2S2O3, solution.
                                    Responding variable   : Rate of reaction.
Controlled variables   : Volume and concentration of sulphuric acid, H2SO4

Operational definition : The time taken for the mark “X” to disappear from sight when the sodium thiosulphate, Na2S2O3, solution react with sulphuric acid, H2SO4
The rate of reaction is measured by how fast the 'X' is hidden by the yellow precipitate

Apparatus                    : 50cm3 measuring cylinder, 100cm3 conical flask, 10cm3 measuring cylinder, stopwatch

Materials                     : 0.2 mol dm-3 sodium thiosulphate, Na2S2O3, solution, 0.1mol dm-3 sulphuric acid, H2SO4, distilled water, white paper marked “X” at the centre

Procedure                    :-

1.      50cm3 of 0.2 mol dm-3 sodium thiosulphate, Na2S2O3, solution is measured with a 50cm3 measuring cylinder and is poured into a conical flask.
2.      The conical flask is placed on the “X” mark on the centre of a piece of white paper.
3.      Using a 10cm3 measuring cylinder, 5cm3 of 0.1mol dm-3 sulphuric acid, H2SO4 is measured.
4.      The sulphuric acid, H2SO4 is immediately and carefully poured into the conical flask containing 50cm3 of sodium thiosulphate, Na2S2O3, solution. At the same time, the stopwatch is started.
5.      The conical flask is shaken slowly throughout the experiment on the white paper.
6.      The mark “X” is observed vertically from the top part of the conical flask through the solution as shown in the figure.
7.      The stopwatch is stopped quickly as the mark “X” on the white paper is no longer visible.
8.      The time taken, t, for the mark “X” to disappear from sight is recorded
9.      Steps 1 to 8 are repeated four more times using different volumes of 0.2 mol dm-3 sodium thiosulphate, Na2S2O3, solution which is diluted with different volumes of distilled water to form 50cm3 of solution as shown in the table. Whereas the other conditions remain unchanged.
10.  The results are recorded in a table.

Data and observations            :-

Interpreting data         :-

1.      Based on the results, two graphs are plotted.
(a)    The graph of the concentration of sodium thiosulphate, Na2S2O3, solution against the time taken for the mark “X” to disappear from sight.
(b)   The graph of the concentration of sodium thiosulphate, Na2S2O3, solution against 1/time.
2.      Based on the graph plotted, determine the relationships between the concentration of sodium thiosulphate, Na2S2O3, solution with   
(a)    The time taken
-          As the concentration of sodium thiosulphate, Na2S203, solution decreases, a longer time is needed for mark ‘X’ to disappear from sight.  Therefore, as the concentration becomes lower, the rate of reaction also decreases.
(b)   1/time
-          The rate of reaction is high when the concentration of sodium thiosulphate, Na2S2O3, solution is high. Concentration of sodium thiosulphate, Na2S2O3, solution is directly proportional to 1/time or rate of reaction.
3.      Deduce the effect of the concentration of a reactant on the rate of reaction.
-          The relationship between the rate of reaction and the concentration of sodium thiosulphate, Na2S2O3, solution is, when the concentration of a reactant increases, the rate of reaction increases.

Discussion                   :-
           
1.      Write down the ionic equation for the reaction between sodium thiosulphate, Na2S2O3, solution and sulphuric acid, H2SO4.
-          S2O32-(aq)   +   2H+(aq)   →   S(s)   +   SO2(g)   +   H2O(l)
2.      Name the pungent smell which is released throughout the experiment?
-          The pungent smell produced is sulphur dioxide gas.
3.      What is represented by 1/time?
-          1/time is a measurement of the rate of reaction.
4.      Why is the same size of conical flasks is used throughout the experiment?
-          Conical flask of the same size and shape are used in this experiment. If a bigger conical flask is used, the time taken for the mark “X” to disappear from sight becomes longer. This is because bigger conical flask has a larger base area. The mixture of 50 cm3 solution becomes shallower. A bigger amount of yellow precipitate is needed to turn the mark “X” invisible from sight.
5.      Hydrochloric acid, HCl with the same concentration is used to replace sulphuric acid, H2SO4 in the experiment.
(a)    How does it affect the rate of reaction?
-          If the experiments is repeated using the same concentration of hydrochloric acid, HCl, to replace sulphuric acid, H2SO4, the rate of reaction will decreases.
(b)   Explain your answer in 5 (a).
-          This because hydrochloric acid, HCl, is a strong monoprotic acid whereas sulphuric acid, H2SO4, is a strong diprotic acid. Although the concentration of acids is the same, the concentration of hydrogen ions in sulphuric acid, H2SO4, is twice the concentration of hydrogen ions in hydrochloric acid, HCl.

Conclusion                  : Hypothesis is accepted. The rate of reaction will increase if the concentration of sodium thiosulphate, Na2S2O3, solution increases.
When the concentration of sodium thiosulphate, Na2S2O3, solution increases, the rate of reaction increase.


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12 comments:

  1. Sahaya7 February 2014 at 06:44

    Elizabeth, terima kasih post entri ni..

    Nice work. Nk tanya, peka ni sume awk buat sendiri atau dah bncang dgn cikgu?

    ReplyDelete
    Replies
    1. Unknown9 February 2014 at 08:40

      Dear Sahaya,
      sorry lambat reply. peka ni semua saya buat sendiri, jawapan ada yang ambil dari buku rujukan, ada yang sudah bincang dengan cikgu. peka ni sudah pun hantar bagi cikgu, cikgu tidak minta buat balik, so i guess everything's okay. haha sorry lagi atas kekurangan yang ada dan masih ada beberapa soalan pekayang belum berjawab, akan saya cuba isi semula post ni kelak. thanks

      Delete
  2. Unknown11 February 2014 at 03:50

    terima kasih untuk entry ni :)

    ReplyDelete
  3. creampuffy :)13 February 2014 at 09:15

    thanks a bunch.. this help me alot :)

    ReplyDelete
  4. RainbowSparkle23 January 2016 at 07:52

    Thnks a lot, :)

    ReplyDelete
  5. Unknown10 February 2016 at 02:06

    U help me to finished it !! Thankss

    ReplyDelete
  6. Unknown11 March 2016 at 21:32

    Thank you very much . But where are the table and graphs ?

    ReplyDelete
  7. Unknown11 March 2016 at 22:05

    This comment has been removed by the author.

    ReplyDelete
  8. Fina12 November 2018 at 04:25

    Ada safety precaution x?

    ReplyDelete
  9. Zelggx :v21 January 2019 at 20:36

    Terima kasih banyak banyak

    ReplyDelete

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