AIM:
The experiment is to investigate the effect of the change in the concentration of Hydrogen peroxide and sodium thiosulphate on the rate of reaction between potassium iodide (KI), hydrogen peroxide, Sodium thiosulfate (Na2S2O4) under acidic condition.
Introduction:
The rate of reaction can be defined as the rate at which the reactants are consumed of the rate at which product is formed.
It is the ratio of the concertation of reactant used of concentration product to time, it measured in mol.dm-3.S-1.
This can be expressed as Rate of reaction = - (∆[reactant])/∆time = (∆[product])/∆time
This implies that the rate of reaction is directly proportional to the concentration of reactant/product but inversely proportional to the
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THEORY OF THE EXPERIMENT
In this experiment change in the volume of reagents by diluting with water is used as change in the concentration and reciprocal of the time taken for the appearance of blue black colour as the reaction rate.
Equation of reaction
H2O2 (aq) + 2H+ (aq) +2I- (aq) I2 + 2H2O
Hypothesis
Hypothesis 1: Decrease in concentration of hydrogen peroxide (H2O2) decreases the rate of reaction (that is, increases the time for reaction to come to completion). In the reaction between potassium iodide (KI), hydrogen peroxide, Sodium thiosulfate (Na2S2O4) under acidic condition.
Hypothesis 2: Decrease in the concentration of potassium iodide decreases the rate of reaction (that is increases the time for the reaction to come to completion). In the reaction between potassium iodide (KI), hydrogen peroxide, sodium thiosulfate (Na2S2O3) under acidic condition.
Apparatus:
The apparatus used in this experiment are as follow: 50cm3 measuring cylinder 25cm3 measuring cylinder 100cm3 beaker White
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20 20 5 10 10 1.00 15.81 0.06
Graph
Discussion:
From the table and graph above it was observed that decrease in the concentration of hydrogen peroxide increased the time for the blue black colouration to appear, which gave rise to decrease in the rate of the reaction. The volume of distilled water added as shown in the table was to reduce the concentration of the hydrogen peroxide.
The same trend was observed in the dilution of potassium Iodide.
In the graph the volume of hydrogen peroxide was used as the concentration since concentration is proportional to volume.
Conclusion
It was clearly observed that the decrease in the concentration of hydrogen peroxide lead to increase in the reaction time and also decrease in the rate of the reaction. Also the decrease on the concentration decreases the rate of the reaction. The two graphs were straight line graphs with positive slopes.
So effective collision for a chemical reaction depends directly on the concentration of the reagent, that is, the crowdedness of the reacting molecules which increases reaction time and vice versa.
References