What are the chemical clock?
The chemical clock is a scenario where reacting chemical compounds bring a sudden observable event after a time delay that can be set relatively precisely by adjusting the concentrations of reactants. The event is often marked by a change in color, but it can have some other form, such as the production of gas causing the fizz. In some cases, the change is cyclical and includes a solution that regularly switches between two or more states, usually marked with different colors. Two colorless solutions are mixed and after the pause, the resulting solution suddenly turns dark blue. In the most common version of the experiment, one solution contains a dilute mixture of hydrogen sulfuric acid and hydrogen peroxide and the other a mixture of potassium, starch and sodium thiosulpha. When mixing solutions, elementary iodine is released from potassium iodide, but faster yodus intermediate reactions and sodium thiosulpha turn it back into colorless iodide ions. When all the thiosulphate was used, iodine is able to react with starch to form a dark blue compound.
cyclic or oscillation reactions of chemical clocks are particularly fascinating. Normally chemical reaction takes place in one direction until the equilibrium point is reached. Then there will be no further change without any other factor intervention, such as a change in temperature. The oscillation reactions were initially mysterious, because they seemed to resist this rule spontaneously by removing from the balance and repeatedly returning there. In fact, the overall reaction proceeds towards balance and remains there, but in the process of one or more reaction components or intermediate products differ in a cyclic manner.
In the idealized oscillation chemical clock, there is a reaction that creates a product and other reactions that use this product, while the product concentration determines which reaction is. When the concentration is low, the first reaction occurs, creating more products. However, an increase in product concentration will trigger a second reaction,It reduces concentration and stimulates the first reaction. This results in a cycle in which both competitive reactions determine the product concentration, which in turn determines which reaction will take place. After several cycles, the mixture reaches balance and the reaction stops.
One of the first cyclic chemical clocks watched William C. Bray in 1921. It was a reaction of hydrogen peroxide and iodat salts. Investigation Bray and his student Hermann Liebhafsky showed that iodate reduction to iodine, oxygen production and iodine oxidation back to Joodate, took placee periodically with cyclic peaks in oxygen production and iodine concentration. This became known as the Bray-Liebhaf reaction.
In the 1950s and 60s. If the reaction is performed by Belousov-Zhabotinsky or Bz using a thin layer of chemical mixture, an observable purpose isInek with small local fluctuations in reactants concentrations leading to complex spiral and concentric patterns. Chemical processes take place very complex and include up to 18 different reactions.
Scientific instructors Thomas S. Briggs and Warren C. Rauscsher, who use the above reactions as a basis, created an interesting three-color oscillation chemical clock in 1972. The Briggs-Rauscher reaction has solutions that have a solution that has a solution that changes from colorless to light brown to dark blue. If it is set carefully, there may be 10-15 cycles before settling into a dark blue color.
Unusual chemical clock, which includes shape changes rather than color, is the reaction of mercury that beats the heart. A drop of mercury is added to the potassium dichromate solution in sulfuric acid, and then an iron nail is placed near the mercury. The film of mercury and sulfate is formed on a drop, reduces surface tension and causes it to extend and touch withe iron nail. When this happens, electrons from the nail reduce the sulfate of mercury and back to the mercury, restore the surface voltage and cause the blob to download again and lose contact with the nail. The process is repeated many times, resulting in a cyclical shape change.
Chemical hours of hours are an area of ongoing research. In particular, cyclic or oscillation reactions are very interesting about the study of chemical kinetics and self -organization systems. It has been speculated that the reaction of this type could be involved in the origin of life.