Aim :
To study the effect of a catalyst on the rate of reaction.
Problem statement : How does a catalyst affect the rate of reaction?
Hypothesis : The presence of a catalyst increases the rate of
reaction.
Variables :-
Manipulated variable : Presence or absence of a catalyst.
Responding
variable : Rate of reaction.
Controlled variables : Volume and concentration of hydrochloric acid,
HCl, mass of zinc powder
Operational definition : The changes of gas volume are measured in
intervals of 30 seconds when a catalyst is presence or absence when zinc power,
Zn, is added to hydrochloric acid, HCl.
Apparatus : 50cm3 measuring cylinder, 100cm3 conical flask,
rubber stopper with delivery tube, burette, retort stand with clamp, stopwatch,
basin, electronic balance
Materials : 0.1 mol dm-3 hydrochloric acid, HCl, zinc
power, 0.5mol dm-3 copper sulphate, CuSO4, solution, water
Procedure :-
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1.
50cm3 of 0.1 mol dm-3 hydrochloric acid,
HCl, is measured with a measuring cylinder and the poured into the conical
flask.
2.
5g of zinc power, Zn (Set I) is weighed
with an electronic balance.
3.
The basin and the burette are filled
with water. The burette is inverted in the basin and clamped vertically with a
retort stand.
4.
The water level in the burette is
adjusted so that the reading of the water level is almost at 50cm3.
5.
Pour the zinc powder, Zn, that have been
weighed into the conical flask which filled with hydrochloric acid, HCl.
6.
The conical flask is immediately covered
with a rubber stopper which is joined to the delivery tube. The gas released been
channeled into the burette and the stopwatch is started at the same time.
7.
The conical flask is shaken slowly throughout
the experiment.
8.
The burette readings are recorded at
intervals of 30 seconds for 5 minutes.
9.
Steps 1 to 8 are repeated by adding 5cm3
of 0.5mol dm-3 copper sulphate, CuSO4, solution (Set II) into the conical flask.
The other conditions remain unchanged.
10. The
results are recorded in a table.
11. The
volume of hydrogen, H, gas collected are measured.
Data and observations :-
Interpreting data :-
1.
Based on the results, a graph of the
total volume of hydrogen gas, H2, collected against time for sets I and II is
drawn on the same axis.
2.
Based on the graph plotted,
determine
(a)
The overall average rates of reaction
for
(i)
Set I
-
(ii)
Set II
-
(b)
The rates of reaction at 90th
seconds
(i)
Set I
-
(ii)
Set II
-
3. Compare
the rates of reaction for both sets of experiments.
Discussion :-
1.
Write down the chemical equation for the
reaction between hydrochloric acid, HCl, and zinc powder.
-
2HCl + Zn à ZnCl2 + H2
2.
What
the effect of copper sulphate, CuSO4, solution on the rate of reaction.
3.
A student found that the volume of hydrogen, H2, gas collected for both
sets of experiments was the same. What can you conclude about the presence of
copper sulphate, CuSO4, solution and the total volume of gas collected?
Conclusion : Hypothesis is accepted. The presence of a
catalyst increases the rate of reaction.
Where is the tabulation of data ?
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