Limiting Reactant Demo

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Initial Procedures

Separate into groups of 2 with 1 group of 3 if needed.
Each group needs to obtain a bag labelled A and one labelled B.
Each group get a balance and make sure it is zeroed.
Mass each bag and put masses in following blanks.

Mass of A: __________________ g Mass of B: ______________

Background Information and more procedures

We are going to use two Substance (A and B) as our reactants. These reactants will form products (actually different groupings of A & B) by the following chemical reaction:

4 A + 3 B --> 1 A₂B₁ + 2 A₁B₂

Question: With your knowledge of the mass of each bag (do not do any counting) and how these material are going to combine (from above chemical reaction),

Which Substance A or B with run out first (write guess in here): _____________________

Now open each bag and count how many items are in each bag and record that number here

Number of A in bag: ___________________ A Number of B in bag: _____________________B

Question: Again without calculating and from your knowledge of how many items you have of each (and chemical reaction),

Which Substance A or B will run out first (write guess here): ________________

Now, from what you just guesses (number guess not mass guess), determine how many of the other reactant you need to completely react all of items of the substance you think will run out first (you will be use ratios or we call molar ratios in balanced chemical reaction). Please show the calculation in the following space (remember Dimensional Analysis showing work rules):

Now fill in the following information:
a. Which substance you assumed all of it reacted: ______________
b. What were the number of the other reactant needed to react all the substance in a. _____________________.

Assumed: ____________ goes to completion.

Since I have ___________ (reactant not completely used up in reaction) initially and I need ______________ numbers of _______ (reactant not completely used up) to completely react all of _________(substance that you did assume completed reacted), therefore, _________________ is the limiting reactant (one that runs out first).

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