Iodine clock reactions

The "iodine clock" reaction Rate of reduction of iodate by sulfite was increased... 

I. Title Chemical Kinetics An Iodine Clock Reaction... 

ChemicalEducation Resources, Inc., "ChemicalKinetics iodine Clock Reaction," Palmyra, PA, 1988. 

Ealy, "The Starch-Iodine Clock Reaction," Chemical Demonstrations, A Sourcebook for Teachers, Vol. 1 (American Chemical Society, Washington, DC, 1988), pp. 107-108. 

Morris, "A New Twist on the Iodine Clock Reaction Determining the Order of a Reaction," J. Chem. Educ., Vol. 76,1999,530-531. 

Concentration. The iodine clock reaction is a convenient reaction for observing concentration effects. The reaction is between potassium iodate, KI03, and sodium bisulfite, NaHS03 the net ionic reaction is given by the following equation. 

In general, we expect that doubling the concentration of a reactant will approximately double the rate of reaction. Was this expectation justified in the iodine clock reaction ... 

The time required for a definite small amount of iodate to be consumed will be measured by determining the time required for the iodine produced by the reaction (as I3) to oxidize a definite amount of a reducing agent, arsenious acid, added at the beginning of the experiment. Under the conditions of the experiment, arsenious acid does not react directly with iodate at a significant rate but reacts with iodine as quickly as it is formed. When the arsenious acid has been completely consumed, free iodine is liberated, which produces a blue color with a small amount of soluble starch that is present. Since the blue color appears rather suddenly after a reproducible period of time, this series of reactions is commonly known as the iodine clock reaction. 

Starch is an organic compoimd that reacts immediately with iodir to form a dark blue compoimd. The starch-iodine clock reaction involves timing the rate of formation of this blue compound after mixing two solutions. One solution reacts to produce iodine, and the other solution contains starch. 

MiniLab 3 Predict the effect of each of the following on the speed of the starch-iodine clock reaction. 

Starch-Iodine Clock Reaction 220 18.2 A Synthetic Aroma 646... 

IIIB) Dutt, A. K., Banerjee, R. S. Oscillating Iodine Clock Reaction in Presence of Chloride 1981-2 Ions. J. Indian Chem. Soc. 58, 717-719... 

Experienced chemistry teachers are likely to know this as a classic reaction, but it is very good, so no apologies are made for its inclusion. The iodine clock reaction can be used as a... 

Table 5.1 Reaction mixtures for the iodine clock reaction...

The iodine clock reaction makes a good demonstration. To set this up, make the same reaction mixtures as above, but enlarge the volumes and carry out the reactions in conical flasks so the colour change can be seen easily. Set the flasks against white backgrounds (such as pieces of card or a white screen). Ask students to help -have a timer for each reaction and ensure that the potassium peroxodisulfate solution is added simultaneously to each flask. 

The first report about the effect of ultrasound to chemical reactions is frcrni 1927 by Richards and Loomis, involving rate studies on the hydrolysis of dimethyl sulfate and the iodine clock reaction (the reduction of potassium iodate by sulfurous acid) (Richards and Loomis 1927). With some exceptions (Porter and Young 1938 Renaud 1950), the field was relatively overlooked for nearly 60 years. However, in the 1980s, sonochemistry was reborn and began to be widely used in many different areas. The reason for this growth was the availability of inexpensive and tpropriate laboratory equipment, such as ultrasonic cleaning baths (low intensity) and ultrasonic probes (high intensity). 

Probably the most famous clock reaction is an iodine clock reaction, a redox reaction involving hydrogen peroxide and acidified iodide ions. The iodine is not seen when the reactants are first mixed because it is being converted to colourless iodide ions in a reaction with another reactant. The reaction of the acidified iodide ions with hydrogen peroxide is ... 

A classic chemical reaction/demonstration called the iodine clock reaction is usually measured this way.)... 

The iodine is then titrated with the thiosulfate solution as detailed in Chapter 17 (p. 516). Finally, potassium iodate is used as an oxidizing agent in the intriguing iodine clock reaction commonly used as a demonstration of limiting reagents and as a system to exemplify the determination of a rate law (see Problem 18.52). 

In the iodine clock reaction, a colorless solution suddenly changes to a blue-black iodine—starch complex in a predetermined amount of time (dependent upon the temperature and the concentrations of the reactants). The iodine is produced by the reaction of iodic acid and hydrogen iodide as represented in the following unbalanced equation. Identify the oxidiang and reducing agents in this reaction and balance the equation. 

The expression fast reactions is obviously ambiguous. We can clarify its usage here by referring to the familiar iodine clock reaction (Landolt reaction). If the reducing agent is denoted by R and its oxidized form by Ox, the principal reaction steps of the Landolt reaction may be written as... 

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