Iodine Clock Reaction Essay

In reference to the collision theory, molecules act as small spheres that collide and bounce off each other, transferring energy among themselves when the collide. In order for a reaction to occur, there must be collisions between molecules. Through experimentation, factors are discovered that influence the reaction rates of chemical reactions include the concentration of reactants, temperature, surface area, the physical state of reactants, and a catalyst. This experiment regarding the factors that affect reaction rate tests the effects of increased concentration and

A clock reaction is characterised by an abrupt colour change following an established time lag (Lente et al, 2007). The induction period in a clock reaction is a result of low concentrations of the clock chemical (i.e. the chemical that enables the final reaction). The induction period ends after the total consumption of a limiting reagent, which initiates a short increase in the rate of product formation, resulting in a visible colour change (Schmitz, 2010)(Lente et al, 2007). The reaction rate of clock reactions is subject to factors including temperature, concentration, catalysis and inhibition. These factors can be manipulated, thus changing the length of the induction period in a ‘clock-like’ manner (Shakhashiri, 1992).

“The iodine clock reaction was discovered by the Swiss chemist Hans Heinrich Landolt in 1886.” (Scilearn, 2017). There are many variations of the iodine clock reaction but they all involve two colourless solutions being mixed and after a specific period of time, the mixed solutions turn dark blue. The iodate variation of the clock reaction involves the reaction between iodate ions. These being, IO3-, hydrogen sulfite ions, HSO3-, and hydronium ions, H+. To ensure the blue colour change, starch is needed to be added to the solution, reacting with I2. The delay in colour change occurs because as soon as I2 is formed, it immediately reacts with any HSO3- still present and is converted into colourless I-. After all the HSO3- has been consumed, the concentration of the I2 increases and begins reacting with the starch. This is why the dark blue colour is suddenly present. The reaction of the starch reacting to turn the solution a deep blue colour. The reaction occurs in two steps. The first step generates iodide ion (I in Equation 2, which occurs slowly and is the rate determining step. “A rate determining reaction is the slowest step in a reaction mechanism and is assumed to be equal to the overall reaction rate because the reaction cannot go faster than the slowest step.”(Webcache.googleusercontent.com, 2017 ).

The standard rate law for the Iodine Clock reaction, is a first order reaction for KIO3 and a second order reaction for NaHSO3. To determine this you must substitute the values into the equations and whichever produces a straight line graph determines whether it is a first or second order reaction. In graph 1. It shows that KIO3 is a second order reaction, this is due to the second order reaction graph being straighter than the first order graph. This meaning the reaction proceeds at a rate proportional to the square of the concentration,

Clock reactions are among the most visually entertaining demonstrations of chemistry. Simply put, a clock reaction is one where two substances are mixed and there is a time delay where there is no visually discernable change in the system. During this delay, one of the chemical species, the clock chemical, has a very low concentration. The end of this induction period is marked by a rapid increase in concentration of the clock chemical (S.J. Preece et al., 1999). This rapid increase in concentration is what triggers effects such as a sudden colour change.

Introduction: The rate of a reaction is the speed at which a chemical reaction happens. If a reaction has a low rate, that means the molecules combine at a slower speed than a reaction with a high rate. Some reactions take hundreds, maybe even thousands, of years while others can happen in less than one second. (Chem for Kids, 2016). Reactions require collisions between reactant molecules or atoms. The formation of bonds requires atoms to come close to one another. New bonds can form only if the atoms are close enough together to share electron. Higher temperatures make the collisions between molecules more violent. The higher temperatures mean higher velocities. This means there will be less time between collisions. The frequency of collisions will increase. (Chem, 1999) H2O2 is the chemical formula for hydrogen peroxide. The decomposition of hydrogen peroxide will break down into oxygen and water.

This image explains that the higher the temperature, the concentration, and the pressure the faster the rate of the reaction is.

In this experiment it was observed that not all chemical reactions occur at the same rate. Chemical reactions occur when one or more substances are changed into other substances. The properties of a chemical reaction require three things. First, they need a source of energy for molecules to encounter each other. Second, they require to proceed at a steady rate. Third, they must proceed in a particular direction until they reach equilibrium. There are two types of chemical reactions that can occur: endergonic and exergonic reactions. In these reactions there are both reactants and products. In exergonic reactions the reactants (starting materials of a reaction) are higher than the products (results of a reaction). This is opposite for endergonic

To determine what factors influence the rate of a chemical reaction and to make predictions based on these

affect the rate of almost all chemical reactions that take place in living organisms. (Lab #4:

In this experiment we tested the effects that enzymes and substrate have on chemical reaction rates, which is the rate at which chemical reactions occur.. This experiment tested how different concentrations of enzyme and substrate affected the light absorption measurements on a spectrophotometer. The experiment also tested how temperature affected the light absorption, and in a separate test, the effect of the enzyme inhibitor hydroxylamine was also tested. In the first test conducted, 3 different concentrations of enzyme, and three different concentrations of substrate were measured in a spectrophotometer. For the enzyme and the substrate, the measurements got higher as the concentrations were higher, but the over measurements of the substrate were smaller than those of the enzyme. In the second test conducted, the medium concentration enzyme was tested under the temperatures; 4°C, 23°C, 37°C, and 60°C. The measurements in this test got higher as the temperature got higher, but did the measurements under 4°C were overall significantly higher than the other temperature measurements. Lastly, the last test conducted showed that the measurements of the substance with 0 and 1 drop of hydroxylamine inhibitor went up, but the measurements of the enzyme with 5 drops of hydroxylamine inhibitor stayed rather low and did not change much. In conclusion, these experiments showed that chemical reaction rates are sped up with higher concentrations of enzyme, substrate,

Therefore, the experimental rate law processes some degree of accuracy. Rate laws are used to define the rate of reaction

It caused the particles to move faster inside each reactant, and caused them to combine quicker to form this deep indigo substance. Some errors that could have occurred in this lab are the use of improper techniques. Students could have heated up the reactants too much and taken the wrong temperature which would cause the Starch to break down if the temperature was just a meer 5o C too

Two catalyst reactants are used in the experiment, thiosulfate and starch, to dictate the time of reactions.

The key aim of this experiment was to determine the rate equation for the acid-catalysed iodination of acetone and to hence consider the insinuations of the mechanism of the rate equation obtained.