The “clock reaction” is a reaction famous for its dramatic colorless-to-blue color change, and is often used in chemistry courses to explore the rate at which reactions take place. The color change occurs when I2 reacts with starch to form a dark blue iodine/starch complex.
What is the conclusion for iodine clock experiment?
Conclusion Based on the data acquired from this experiment, we can see a trend in the rate of reaction when concentration of its reactants are manipulated. The relationship between concentration of hydrogen peroxide and rate of reaction fits a linear regression line as seen in the graphs above.
What happens during the iodine clock reaction?
Two colorless liquids are mixed together and after a few moments the mixture turns a dark blue color. There are actually a couple of simple chemical reactions going on at the same time to make this “clock reaction” occur.
What does iodine do in an experiment?
Using iodine to test for the presence of starch is a common experiment. A solution of iodine (I2) and potassium iodide (KI) in water has a light orange-brown color. If it is added to a sample that contains starch, such as the bread pictured above, the color changes to a deep blue.
Why is it called iodine clock reaction?
The iodine clock reaction is a favorite demonstration reaction in chemistry classes. … The reaction is called a clock reaction because the amount of time that elapses before the solution turns blue depends on the concentrations of the starting chemicals.
How does a clock reaction work?
This clock reaction uses sodium, potassium or ammonium persulfate to oxidize iodide ions to iodine. Sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color.
What is a clock reaction in simple terms?
A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount.
What is iodine used for?
Iodine is a mineral found in some foods. The body needs iodine to make thyroid hormones. These hormones control the body’s metabolism and many other important functions. The body also needs thyroid hormones for proper bone and brain development during pregnancy and infancy.
What is the activation energy of the iodine clock reaction?
Iodine-Clock Activation Energy
(1/T) for the iodine clock reaction should reveal a slope of about -6230. Thus, (-Ea/R) = -6230. Using an ideal gas constant of R = 8.314 J/K. mol gives Ea = 6800 * 8.314 = 51,800 J/mol, or 51.8 kJ/mol.
What are the two reactions that occur in the iodine clock reaction?
There are two reactions occurring in the solution. In the first, slow reaction, the triiodide ion is produced . H2O2(aq) + 3 I–(aq) + 2 H+ → I3– + 2 H2O. In the second, fast reaction, triiodide is reconverted to iodide by the thiosulfate.
What is the overall order of the iodine clock reaction?
The rate of reaction is first-order in potassium iodine. For the qualitative option, the details of the mechanism are not revealed to the students in order to have the students focus on the kinetics concepts of changing the concentration of one reactant versus time or reaction.
Is the iodine clock reaction exothermic or endothermic?
In terms of thermodynamics, this reaction is exothermic and should occur spontaneously.
Why is iodine used to test starch?
In the presence of starch, iodine turns a blue/black colour. It is possible to distinguish starch from glucose (and other carbohydrates) using this iodine solution test. For example, if iodine is added to a peeled potato then it will turn black.
Why does iodine only test for starch?
Chemical Test for Starch or Iodine
Iodine – KI Reagent: Iodine is not very soluble in water, therefore the iodine reagent is made by dissolving iodine in water in the presence of potassium iodide. … Starch amylopectin does not give the color, nor does cellulose, nor do disaccharides such as sucrose in sugar.
Why does iodine not react with glucose?
Even though they are both carbohydrates, iodine will not change colors when it gets exposed to sugar. This is because starch is made up of many, many sugar molecules chained together. Only the long chains found in starch are able to interact with the iodine.