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General Chemistry

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Chemical Reactions

Question
10 out of 15
 

Passage 1

Information regarding the amounts of substances that actually react to form the products are of extreme help. Analyzing reactions and having the balanced equations help chemists to determine the correct and optimum proportions of reactants to be used. There are various other factors besides the amount of reactants, which determine the efficiency of reactions.

Experiment 1

Student 1 used 40.5 g of aluminum and 80 g of Fe2O3 for Reaction I. A second student conducted the same reaction with a different amount for one of the reactants. The second student used 40.5 g of aluminum, and 90 grams of Fe2O3. A third student also conducted the same reaction with 54 g of aluminum and the same amount of Fe2O3 used by the first student.

Experiment 2

Reaction II involved the production of Al2O3 from aluminum hydroxide This was done by heating aluminum hydroxide.


Experiment 3


In Experiment 3, which of the following is the limiting reagent?

A Fe2O3 because there is only 1 mole of it
B CO because of its gas phase
C Fe because of its insufficiency
D Cannot be determined without more data

Ans. D The reactant coefficients in a balanced equation cannot be used to determine the identity of the limiting reagent. Without comparing the amounts of reactants that are actually present, we cannot determine the identity of the limiting reagent. CO being a gas has nothing to do with being the limiting reagent for the given reaction. Choice C is not logical, because it is a product. The best answer is that we cannot determine the identity of the limiting reagent, if any, without any data regarding the amount of reactants used.

Chemical Reactions Flashcard List

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