PURPOSE The objective of this experiment is to perform a combination (synthesis)
ID: 497880 • Letter: P
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PURPOSE The objective of this experiment is to perform a combination (synthesis) reaction by combining elemental zinc with elemental iodine. We will explore the concept of limiting reagents, theoretical yields and percent yields by measuring analytically the masses of the reactants and product. From these data we will calculate the empirical formula for the zinc iodide and ultimately we will be able to verify the Law ofConservation of Mass MATERIALS AND EQUIPMENT 20-mesh granular zinc metal, solid iodine, I20s, methanol. Centigram balance, analytical balance, plastic wei ghing boats, glazed weighing paper BACKGROUND in color and is zinc metal consists of monatomic zinc atoms that is a silvery gray insoluble in methanol. In this experiment, is in the form of small with purplish black Elemental iodine is a nonmetal which is a shiny a purple it is quite It sublimes (solid- gas relatively easily to form vapor, and atoms reactive. Elemental iodine is a diatomic molecule meaning that two iodine form of are joined to each other by a single covalent bond. It is soluble in methanol, forming a dark colored solution. compound is one the simplest A reaction between two elements to form a binary amount of type of combination reactions. In this experiment, we will combine an excess gentle elemental zinc with elemental iodine in methanol as a solvent, supplement ed with heating (refluxing) to form the ionic compound of zinc iodide. The corresponding reaction can be written like this: Znos) I20s) znl20s. However, for this experiment, we will calculate moles of each reactant as if they were both monoatomic (not nature. Therefore we will set up a scheme to determine the simplest formula for zn will where y/x represents molar ratio (mole Vmole Zn) or mass ratio (g V g Zn). We determine the value of coefficients x and y by carefully measuring the masses and iodine used that reacted. The mass ratio is related to mole ratio by following equations mol I Molar mas I g I mol Zn Molar mas Zn g Zn. gl g I/mol mol I mol Zn g Zn/mol Zn g Zn According to our experimental scheme, all of the iodine i consumed since it is the limiting reactant for this combination reaction. Moreove when iodine is consumed completely the dark brown color of solution fades to pale yellow or solution. This indicates the completion of the reaction. The ma of zinc (insoluble methanol can be measured after isolating and drying leftover zinc. the other hand, the mass of zine can e determined by subtracting mass of the unreacted zinc from the total the have enough information to calculate the empirical formula for the product. Finally weExplanation / Answer
Formation of ZnI
Zn + I2 --> ZnI2
2) Zn in insoluble in methanol, whereas, zinc iodide is soluble in methanol. Thus the solubility of the two components are used to separate Zn from ZnI2
3) If leftover zinc in transferred to the product. Mass of Zn reacted would be greater than actual value. Thus the molar ratio of Zn reacted with ZnI2 formed (I2 consumed) would be higher and the formula would be with higher Zn percent in ZnI2 instead of 1 Zn2+ to 2 I-.
4) Yes, the experiment proved the concept that mass of product equals the mass of reactant reacted in the experiment.
5) If an insoluble non-reactive impurity remained in the flask after the reaction along with the unreacted Zn. the mass of reacted Zn calculated would be lower. Thus the formula would have lower percent of Zn in it than the actual value.
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