Could youu please help e with my lab report? This is a lab for formula and forma
ID: 810763 • Letter: C
Question
Could youu please help e with my lab report?
This is a lab for formula and formation constant determination.
Use the average of the Kf's you found for solutions B2, B3, and B4 to test the validity of the assumption that we made for solution B1; namely that the thiocyanate ion present was nearly completely complexed.
The average i have is 22.7.
Why would it have been difficult to obtain reliable results if the absorbances had been measured at 675 nm?
Explain how the method of continuous variations might be used to determine the stoichiometrics of the following types of reaction:
a) an endothermic reaction between two substances in solution.
b) a reaction between 2 gaseous reactants to produce gaseous products where delta n does not equal 0.
c) a reaction between two strong electrolytes in solution to form a soluble, nonionized product
Explanation / Answer
The method of continuous variations is used to determine the mole ratio of two reactants in a chemical reaction. Typically the mole ratios of reactants and products can be found from a balanced chemical equation, however when the formulas of the products are unknown, experiments can be conducted to discover this ratio.
The method is often applied to whole-sample absorbance measurements but its utility is limited when two or more complexes are present at significant concentrations and have similar absorption spectra.
When given a balanced chemical equation the mole ratios of reactants and products is expressed by the coefficients of those formulas. However, the formula of the reactants and products are not always known. When using the method of continuous variations, the total number of moles is kept constant, but the ratios of the reactants are varied. During the chemical reaction, these reactants will produce some sort of measurable property, be it color, a precipitate, or in this instance, heat.
This experiment involved in the occurence of an endothermic reaction, here the measurable property is the heat absorbed and the temperature change of each ratio in comparison with the starting temperature. The heat that is absorbed is directly proportional to the amount of reaction that is occuring; this means that the temperature change is proportional to the quantity of reactants consumed. When temperature change is found to be at its highest, that identifies that the amount of product formed is at its highest, because this measurable product occurs as a result of maximum consumption of the reactants.
In a chemical equation, the stoichiometric ratio will allow the reaction to consume as many reactants as possible and form as much product as capable, so when the measurable property during a continuous variations experiment reflects the same idea, it is clear that this method is effective in finding the mole ratio.