factors affecting rate of a reaction method only EXPERIMENT

							EXPERIMENT Factors affecting the rate of a reaction


MATERIALS

Chemicals/consumable      Glassware                Equipment
 2M hydrochloric          10 mL measuring         thermometer,-10 - 110oC
  acid                      cylinder                Bunsen burner, tripod and
 0.25 M sodium            100 mL measuring         gauze mat
  thiosulphate              cylinder                bench mat
                           3 x 100 mL beakers      stopwatch
                                                    marking pen

SAFETY

 Sulphur dioxide gas can cause eye and respiratory irritation at high
  concentrations. Work in a well ventilated area and dispose of reaction
  mixtures via a sink in a fume cupboard.
 Hydrochloric acid is corrosive
 Wear safety glasses for this experiment
PURPOSE
To investigate the ways in which an increase in temperature and in the concentration
of reactants affects the rate of a reaction.
DURATION
75 minutes
PROCEDURE
A.   Effect of temperature
1.   Mark a cross on a sheet of paper with a black marking pen
2.   Place a 100 mL beaker on top of the cross. Pour 10 mL of 0.25 M sodium
     thiosulphate solution and 35 mL of water into a beaker.
3.   Record the temperature of the solution.
4.   Add 5 mL of hydrochloric acid and commence timing. Measure the time taken for
     the cross to disappear when viewed from above the beaker.
5.   Pour 10 mL of 0.25M sodium thiosulphate solution and 35 mL of water into
     another beaker. Heat the solution to 40oC. Remove it from the source of heat,
     place it on top of the cross, and immediately add 5 mL of hydrochloric acid.
     Again, measure the time taken for the cross to disappear.
6.   Repeat Step 5 with a third beaker, but heat it to 60oC.
B. Effect of concentration of reactants.
Design an experiment to investigate the effect of varying the concentration of sodium
thiosulphate in the reaction studied in Part A of this experiment. Record the results
of your experiment in a table.
THEORY
Hydrochloric acid reacts with sodium thiosulphate to produce sulphur, sulphur
dioxide gas and water:
              S2O32- (aq) + 2H+ (aq)  S (s) + SO2 (g) + H2O (l)

The sulphur precipitate causes the reaction mixture to become cloudy. The rate at
which the solution becomes cloudy indicates the rate of reaction: the shorter the
period before the cloudiness obscures a cross on a sheet of paper placed under the
beaker, the more rapid the rate of reaction. In this exercise the effect of temperature
and of concentration of one of the reactants on the rate of reaction is studied.
RESULTS
Part A
                          Temperature               Time taken for cross to
                                                          disappear
                                                          (seconds)
                  Room Temp. ___oC

                  40oC

                  60oC

Part B

*Develop your own table for results