Starch Experiment

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Iodine has a brown color, and there is no ions or products with a blue color. Therefore, an assumption is produced that the starch is the key factor to cause the dark blue color. After doing some research, there are two basic types of starch. One is called amylopectin, making up a certain proportion of the starch and it is insoluble in cold water. Thus, the white floating things in Solution B is actually amylopectin, as a type of starch. The other one is called amylose with hydroxyl structure (-OH) like methanol, becoming blue when it meets iodine. After the reaction begins, the first step is IO3- + 3HSO3- → I- + 2HSO4-, which produced many I- ions. Then, the next step is IO3- + 5I- + 6H+ → 3I2 + 3H2O as the rate determining step, which turn…show more content…
The possible reason is that increasing concentration makes more products, especially I2, which reacting with starch causing the color change. For Part 3, the difference in the color of final results is much more obvious. When it is 0℃, the blue color is the darkest. Till 40℃, the color is all blue generally as it is getting slightly lighter one by one. When coming to the 50℃, it shows a purple color and becomes very light purple color in the 60℃ situations. It can be explained by the DP idea mentioned in the second paragraph. When temperature increases, the ability for starch to show color…show more content…
There is a slight difference between rate and reaction rates obviously from the units. Rate is simply 1 divided by the time interval in the unit of s-1. By contrast, reaction rate focus on the change in concentration divided by the time interval in the unit of mol/L/s. However, when talking about the rate of reaction affected by the concentration, for example, Higher concentration in the reactant at first gives more possibility for more successful collisions between particles in correct orientation to make the reaction happens. Therefore, the reaction rate is bigger and it takes less time interval for a complete reaction, so the rate is bigger as well. In both Graph 1.1 and Graph 1.2, the line of best fit has a positive slope, which represent a general trend that when concentration is bigger, both rate and reaction rate is bigger and vice versa. For Part 3, it is finding the relationship between temperature and reaction rate. Temperature is defined as the average kinetic energy. When temperature is increased, the kinetic energy of reactants is increased. As a result, more particles with sufficient kinetic energy for a successful collision means more reactions happening. Thus, reaction rate is higher and it takes less time for the reaction to complete which results in an increase in rate as well. Proof from the Graph 3.1 and Graph 3.2, the general trend,

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