Question

Explain how the method of continuous variations might be used to determine the stoichiometries of the following types of reactions: an endothermic reaction between two substances in solution. a reaction between two gaseous reactants to produce gaseous products where Delta n = 0. a reaction between two strong electrolytes in solution to form a soluble, nonionized product.

Answer 1

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. A specific experiment involved the occurence of an endothermic reation, so the measurable property was the heat taken and the temperature change of each ratio in comparison with the starting temperature. The heat that is taken 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.