Essay On Iodine Clock

Chemical kinetics is the study of rates of chemical processes with respect to reaction rates, result of differing variables, re-arrangement of atoms, formation and intermediates etc (Theodore L. Brown,2010)(Chung Chieh,2016). The study of chemical kinetics is one that is a major importance in chemical research. It is powerful research tool in determining the reaction mechanism of several different reactions in chemistry(The University of Sydney,2002).

Iodine clock reactions are principal examples of chemical kinetics. It was first discovered in 1886 by Swiss chemist Hans Heinrich Landolt(The University of Sydney,2002). Iodine clock refers to a group of reaction in which two colourless solution are mixed together to produce a mixture that

The reaction that forms the basis for the iodine clock reaction are:

Reaction 1: H2O2(aq) + 3 I-(aq) + 2 H+(aq) I3-(aq) + 2 H2O(l)

Reaction 2: I3-(aq) + 2 S2O32-(aq) 3 I- (aq)+ S4O62-(aq)

Reaction 3: 2I3-(aq) + starch (I5- starch complex)+ I-(aq)

(Science Buddies Staff,2015)

These three reaction summarizes the reaction mechanism for the hydrogen peroxide iodine clock reaction. The first step reaction indicates, in an acidic environment hydrogen peroxide oxidizes iodide ions to triiodide ions and forms water( B. Z. Shakhashir,1992).Reaction 1 is the rate determining step as it is the slowest reaction in the overall reaction mechanism( B. Z. Shakhashir,1992). Reaction 2 states that the triiodide ions are reduced back to iodide ions by the thiosulfate ions and forms tetrathionate( B. Z. Shakhashir,1992). Iodide ions are formed in reaction 2 so they are available to react with hydrogen peroxide in equation 1 (Science Buddies Staff,2015). As a consequence of equation 2 being much faster than equation 1, the triiodide ions are consumed as fast as it is formed disabling it from forming a complex with starch in reaction 3(Science Buddies Staff,2015)( B. Z. Shakhashir,1992).All of the thiosulfate ions are consumed in reaction two which is known as the lag period and at this time the triiodide reacts with the starch

Dynamic equilibrium is the state in which reactants are converted to products and products are converted to reactants at an equal and constant rate (Esther Lee,2016). Equilibriums shift or changes can be explained by Le Chatelier 's principle(Esther Lee,2016). Which states If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change(Jim Clark 2002).The kinetics of a reaction can be altered as the position of the equilibrium changes. It can affect the rate of reaction increasing or decreasing it depending on the properties of the reactants or products (Esther