Chemistry Determination Of Crystal Violet

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Objectives: The purpose of this lab is to observe the reaction of crystal violet and sodium hydroxide by looking at the relationship between concentration and time elapsed of the crystal violet. CV+ + OH- CVOH To quantitatively observe this reaction of crystal violet, the rate law is used. The rate law tells us that the rate is equal to a rate constant (k) multiplied by the concentration of crystal violet to the power of its reaction order ([CV+]p) and the concentration of hydroxide to the power of its reaction order ([OH-]q). Rate = k[CV+]p[OH-]q To fully understand the rate law, concentrations of the substances must be looked at first. The concentration is measured in molarity. Molarity is the measure of moles of solute per liter of solution. The rate law helps one find solution's reaction order. If the reaction order is zero, the graphical representation is concentration vs. time, and the slope of the line is the negative rate constant. If the reaction is first order, its graphical representation is seen as ln[A] (natural log of concentration) vs. time, and the slope of its like is also the negative rate constant. Finally, for a second order reaction the graph is shown as 1/[A] (inverse of concentration) vs. time, and the slope of its given line is the positive rate constant. By understanding the rate law and finding the value of the correct rate constant with respect to the order of the reaction, one can determine the half-life of the crystal violet. This is because the crystal violet undergoes a decay reaction with the sodium hydroxide. According to Beer's Law, the absorbance of crystal violet is proportional to its concentration. Therefore, a spectrophotometer connected to a computer interface will determine the absorbance of the crystal violet over a period of time. Knowledge on how to use a spectrophotometer is necessary to

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