Determination of a Rate Law Lab Report Essay

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.

The rate of reaction will be measured by timing how long it takes for the spheres of yeast to sink and float up to the top again.

The rate value changes as the temperature is changed. When the temperature increases by 10˚, the rate of the reaction increases by a factor of 0.12 (12%). This is again changed when the temperature is changed to 10˚ below room temperature. This results in a rate of production of oxygen, which is decreased by a factor of 0.25 (25%).

The results obtained show that the chalk ground to the smallest size was the second longest rate of reaction, the medium size was the longest rate of reaction and the largest chalk size was the shortest rate of reaction. The results of the experiment describe how the surface area of a reactant (the chalk) speeds up the rate of reaction when in contact with another reactant in this instance, the hydrochloric acid.

Kr = Vmax per mg of enzyme x molecular weight x 10-3 mmol µmol-1 x 1 min per 60 seconds.

The slope of this graph, calculated using the average rise / run is also 1. As [S2O8-2] is held constant during these trials, the exponent n for [I-] equals one. The k constant can now be calculated.

Review 3: Text Chemical kinetics is the study of rates and mechanisms of chemical reactions. In our study of chemical kinetics, experimental data identifying the initial concentrations of reactants and the instantaneous initial rates of multiple trials is used to determine the rate law for the reaction, the order of the reactants, the overall reaction order, and the average rate constant. By comparing the instantaneous initial rates and the initial concentrations of the reactants for two trials, it is possible to deduce the order of each reactant. In order to determine the order of A, the two trials must be selected such that the concentration of A changes while the concentration of B is held constant.

Since the concentration for ethanol, C_2 H_5 OH, is much higher than the concentration of K_2 〖Cr〗_2 O_7 , we can apply the treatment of pseudo-order kinetic. The treatment said, when there is a reactant with a high concentration we can remove it from the rate law because when the reactant with the low concentration is used up there will be a very small change to the reactant with the high concentration that we can ignore it like the following: rate= k' 〖[〖〖Cr〗_2 O_7〗^(-2)]〗^x In this experiment, to able to find k we must first find the pseudo-order constant, k', using experimental data. The first step in finding the pseudo-order constant is to find the wavelength that can be used to develop good data.

Since KI is known to speed up a chemical reaction, it was expected to see an indirect linear trend in which the reaction time decreased as the concentration of KI increased. Rather, the data recorded for the volume of KI versus reaction time did not explicitly show an indirect linear trend (Figure 1). Since H2O2 solution is known to have the same affect as KI on a chemical reaction, an indirect linear relationship between the volume of H2O2 solution and reaction time was expected. However, the data recorded for the volume of H2O2 solution versus reaction time did not overtly show an indirect linear trend (Figure 2). Conversely, Na2S2O3 is known to decrease the speed of a chemical reaction.

The Hydrogen Peroxide Iodine Clock can be used to demonstrate the above rates of reaction that lead to chemical equilibrium and explore also the impact of concentration of reactants and temperature on rates. In this experiment, hydrogen peroxide and sulphuric acid are added to a another solution of potassium iodide, sodium thiosulphate and starch. After a lag, the combined solution turns a deep blue colour. The reactions occurring are as follows.

The averaged data for varying the KIO3 concentration is displayed in Table 1 and plotted onto Graph 1. When varying the concentration of KIO3 – 0.134, 0.100, 0.080 and 0.067M – at 30°C, it is apparent that as the concentration decreases, the reaction rate decreases which supports the hypothesis. This can be seen as the lowest concentration of KIO3 was 0.067M with the duration of the reaction being 5.85s. The time decreased approximately 25% for each new KIO3 concentration until it reached 2.95s at 0.134M.

2cm of a solution was tested and added 2 cm of 10% of potassium hydroxide solution and the test tube was shaked.

The purpose of this investigation was to identify and investigate the relationship between various factors and the rate of a reaction. The reaction that was tested, used the combination of a potassium starch solution mixed with a sodium solution, commonly known as the ‘Iodine Clock Reaction’. The two clear solutions are mixed together, which after a given time will form a dark blue solution. The factors used in this investigation are the concentration of two substances and the temperature at which the reaction occurred.

There are several factors that affect the rate of a reaction. Some of them being Pressure (if the reactants are Gases), Temperature, Presence of a Catalyst, Surface Area of the reactant, and Concentration. According to the Collision Theory, during a reaction, particles collide with each other and react if the geometry of the collision is correct. In this Experiment, we will investigate the effect of varying concentrations of Potassium Iodide on its reaction with

Step 4: i = 0 to 30 do: K  0.3  i / 100