The Demonstration And Variance Of The Iodine Clock Reaction

Investigations into the mechanics of chemical kinetics can reveal invaluable information relating to the rates of reaction. There are numerable applications of reaction rates, knowledge in this area is pivotal for industrial, commercial and research sectors. Thus, allowing them the ability to manipulate a variety of factors of chemical reactions with the use of reaction rates. In the scope of the kinetics of clock reactions, there is a range of information that can be obtained about reaction rates (Shakhashiri, 1992).

The importance of conducting this experiment is to discover the rate reaction of the Landolt Iodine Clock. This reaction is used to display the chemical kinetics in action, it was discovered by Hans Heinrich Landolt in 1886. It is where two colourless solutions are combined and no instant change appears but over a certain time delay depending on the factors it will instantly change to a dark blue. The Chemical kinetics of the reaction refers to the rate of the reaction. Different reactions occur at different rates, for example if it is a proton transfer reaction which is an acid-base reaction it will often occur at a faster rate. When the molecules collide in the reaction they must have a sufficient amount of kinetic energy so that the reaction can be initiated. The amount of kinetic energy is generally dependant on the temperature of the reaction, at higher temperatures there is a higher rate of reaction because of the increase of kinetic energy in the reactant molecules.

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.

The rate of a chemical reaction often depends on reactant concentrations, temperature, and if there’s presence of a catalyst. The rate of reaction for this experiment can be determined by analyzing the amount of iodine (I2) formed. Two chemical reactions are useful to determining

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

Comparing the first and second experiments, we see that if [I-] is tripled, the rate triples. Therefore the reaction is first order in [I-].

On day 2, the experimentally determined rate law for this reaction was found to be:

The integrated rate law equations all include the same variables:〖[A]〗_t, representing the concentration of crystal violet at a given time, k, as the true rate constant of the reaction, t, indicating the given time, and 〖⁡[A]〗_o, the initial concentration of crystal violet. By studying the rates of reactions, essentially expressed as how many molecules of reactants are converted to products in a given time period, the determination of the rate law can found. In this experiment, the reaction rate for the reaction, shown in eq. 4, was used to find rate law shown in eq. 5; with k being the rate constant, x being the order for crystal violet, and y being the order for hydroxide.

At 10o C the time of reaction was 75.81 seconds (s). At 20o C the time of reaction was 65.20 s. At 30o C the time for the reaction was 52.80 s. At 40o C the time of reaction was 50.20 s at 50o C the average time of reaction was 52.96 and lastly at 60o C the time of reaction was 41.29 s. This change in time for the reaction to occur can be explained by the collision theory. The collision theory states that for a reaction to take place, the reactant particles must collide at the correct speed and angle. Although this cannot be completely controlled, an increase in temperature will increase the speed of the particles and frequency of collisions inside the liquid reactants themselves and therefore increase the likelihood of reaction to take place. This is why the highest temperature of 60o C had the lowest time for the reaction to take place.

Chemical kinetics involves the examination of reaction rates, which are the speeds of chemical reactions. There are chemical reactions which proceed in long periods of time as well as chemical reactions proceeding in short periods of time. Regarding reaction rates, the reaction order and kinetic rate constant are considered.

Secondary data states that the rate law yielded from the iodine clock reaction was “rate = k[IO3] 1 (Lyle, Department of Chemistry) which was different to the rate law that this investigation obtained. 0.41 [KLO3]^2 [NaHSO3]^2. This would have happened due to the changing of both KIO3 and NaHSO3, and also by adding more distilled water to the mixture which slowed down the reaction rate.

Iodine Clock is the reaction which includes the colorless compounds and after mixture, observance the appearance of color in the solution: dark blue/purple. The color, depending on the temperature and the concentration of the substances which react with one another, appears in a short time interval. Rate of reaction for the experiment is calculated in the equation given below:

Kinetics of chemical reactions is how fast a reaction occurs and determining how the presence of reactants affects reaction rates. In this experiment the rate of reaction for Fe+3 and I- is determined. Because the rate of chemical reactions relates directly to concentration of reactants, the rate law is used to find the rate constant, and calculated with specified temperatures.

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.