Chemical Reactions And Factors That Affect The Rate Of A Reaction

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Reactions occur everywhere, and they may take decades, such as fossils, or only seconds, such as lighting a match to occur. “Chemical kinetics concerns the rates of chemical reactions” and what factors affects these rates (Iodine Clock, 2017). “Temperature, concentration, pressure of reacting gases, surface area of reacting solids and the use of catalysts are all factors which affect the rate of a reaction” (Bbc.co.uk, 2017). This is because they affect the reaction roles and yields of activation energy, product management and reactant management (William, 2017). This is accomplished by “making changes to the concentration, pressure or temperature of a reaction to alter the position of the equilibrium” (Bbc.co.uk, 2017).

Accordingly, the
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It was further identified that typically for every 10oC temperature rise, the reaction rate would double (Del Mundo et al., 2016) (Clark, 2017).

Throughout the Landolt Iodine Clock Reaction, chemical equilibria are clearly demonstrated through the delayed colour change of combining two colourless solutions to form a dark blue solution. The overall chemical reaction for this is as follows:

2IO-3(aq) + 5HSO-3(aq) + 2H-(aq) → I2 + 5HSO-4(aq) + H20(l)
Iodate ions + Bisulfite ions + hydronium ions → Iodine + Bisulfate + water (Iodine Clock, 2017)

The individual steps of the reaction are:
(1) IO3-(aq) + 3HSO3-(aq) → I-(aq) + 3SO4-(aq) + 3H+(aq)
Iodate + Bisulfite → Iodide + Sulfate + Hydronium ions
(2) IO3- (aq) + 5I-(aq) + 6H+aq) → 3I2(aq) + 3H2O(l)
Iodate + Iodide + Hydronium ions → Iodine + Water
(3) I2(aq) + HSO3-(aq) + H2O(l) → 2I-(aq) +SO4-(aq) +3H+(aq)
Iodine + Bisulfite + Water → Iodide + Sulfate + Hydronium ions
(4) I2(aq) + I-(aq) + starch → dark blue starch-I3- complex
Iodine + Iodide + starch → dark blue starch-I3- complex
(Iodine Clock Reaction, 2015)

The first reaction is the rate determining step, and hence, determines the order of the reaction. The equilibria is delayed in this reaction due to any of the iodine produced, immediately reacting with any bisulfite still present, before then being converted into colourless iodide (reaction 2). Therefore, to demonstrate this reaction, the
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