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    Lab Thiosulphate A18 2

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    stamsam
    Reaction between sodium thiosulphate and hydrochloric acid can be studied by pupils themselves. The effect of temperature on the rates of several chemical reactions was referred to in the previous section. Some pupils may require assistance with the two graphs mentioned in the experiment sheet through a confusion of temperature, and times.

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    Lab Thiosulphate A18 2

    Uploaded by

    stamsam
    93 views2 pages
    Reaction between sodium thiosulphate and hydrochloric acid can be studied by pupils themselves. The effect of temperature on the rates of several chemical reactions was referred to in the previous section. Some pupils may require assistance with the two graphs mentioned in the experiment sheet through a confusion of temperature, and times.

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    Reaction between sodium thiosulphate and hydrochloric acid can be studied by pupils themselves. The effect of temperature on the rates of several chemical reactions was referred to in the previous section. Some pupils may require assistance with the two graphs mentioned in the experiment sheet through a confusion of temperature, and times.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    93 views2 pages

    Lab Thiosulphate A18 2

    Uploaded by

    stamsam
    Reaction between sodium thiosulphate and hydrochloric acid can be studied by pupils themselves. The effect of temperature on the rates of several chemical reactions was referred to in the previous section. Some pupils may require assistance with the two graphs mentioned in the experiment sheet through a confusion of temperature, and times.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 2

    A18.

    How do changes in temperature affect the rate of a reaction?

    The chemical system used in section A18.1b is used again in order to study the effect of
    temperature on the rate of a reaction.

    The effect of change in temperature on chemical reactions is an everyday experience. We


    put a cake in the oven in order to speed up desirable chemical changes and we put milk in
    the refrigerator in order to slow down undesirable chemical changes.

    The effect of an increase in temperature on the rates of several chemical reactions was
    referred to in the previous section and it may be appropriate to revise this by one or two
    simple demonstrations. The reaction between sodium thiosulphate and hydrochloric acid is
    easily studied by the pupils themselves.

    What is the effect of temperature on the rate of reaction?

    Procedure

    Practical details are given in Experimental sheet 74. It may be appropriate to discuss ‘ways
    and means’ before practical work is started.

    Some pupils may require assistance with the two graphs mentioned in the Experiment sheet-
    through a confusion of temperature, and times.

    Experiment sheet 74.

    The method for this experiment is the same as that for Experiment 73, except that in this
    case the concentrations of the reacting solutions are kept constant and the temperature of
    the mixture is varied.

    Mix 10 cm3 sodium thiosulphate solution with 40 cm 3 water in a 100 cm3 beaker, and stand
    the beaker over the cross on the sheet of white paper. Add 5 cm 3 hydrochloric acid, with
    stirring, start the stop-clock, and read the temperature of the mixture. Note the time for the
    cross to disappear.

    Repeat the above procedure but this time heat the diluted sodium thiosulphate solution to
    just above 30°C before adding hydrochloric acid. Note temperature and time as before. Then
    find the times required for temperatures of about 40 °C, 50 °C, and 60 °C.

    Results

    In each case, use a reaction mixture of 10 cm 3 sodium thiosulphate solution, 40 cm3 of


    water, and 5 cm3 hydrochlloric acid.
    Plot graphs of:

    1. Temperature (vertical axis) against time (horizontal axis)

    2. Temperature (vertical axis) against 1/t (horizontal axis).

    What do you learn from these graphs?

    Apparatus

    Each pair of pupils will need:

    Experiment sheet 74

    Conical flask, 100 cm3

    Measuring cylinder, 100 cm3

    Measuring cylinder, 25 cm3

    2 beakers, 100 cm3

    Stop-clock or view of laboratory clock with a seconds hand

    Thermometer, -10 to+110 x 1°C

    Bunsen burner and heat resistant mat

    Tripod and gauze

    Sheet of white paper

    Graph paper

    2.0M hydrochloric acid, about 40 cm3

    Sodium thiosulphate solution, containing 37 g per dm 3 (about 0.15M), about 60 cm3

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