Student Exploration: Limiting Reactants (ANSWER KEY)

Student Exploration: Limiting Reactants
Vocabulary: chemical equation, chemical formula, chemical reaction, coefficient, limiting reactant, molecule, product, reactant, subscript
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
Imagine you and your friends are making hot dogs. A complete hot dog consists of a wiener and a bun. At the store, you buy four packages of eight wieners and three bags of 10 buns.
How many total hot dogs can you make? ______________________________________
Which ingredient limited the number of hot dogs you could make? __ _________­___
Which ingredient will you have leftovers of? ____________________ _________
Gizmo Warm-up
Just as ingredients can be put together to make a new food, substances can combine during a chemical reaction to produce new substances. The substances that undergo change are called reactants. The new substances are products.
Sometimes during a chemical reaction, one type of reactant will be used up before the other reactants. This reactant is the limiting reactant. Using the Limiting Reactants Gizmo™, you can determine which reactant is limiting in various scenarios.
To begin, make sure H2 + O2 becomes H2O is selected. The small “2” in H2, O2, and H2O is a subscript. Subscripts represent the number of atoms in a molecule.
Use the sliders to set the number of O2 molecules and H2 molecules to two.
How many hydrogen molecules (H2) are there? _______ Hydrogen atoms? _______
How many oxygen molecules (O2) are there? _______  Oxygen atoms? ___
How many H2O molecules do you think will form when these four molecules react? ______
Click Play (). How many H2O molecules actually formed? _____ 
Activity A:

Water reaction
Get the Gizmo ready:
  • Make sure H2 + O2 becomes H2O is selected.
  • Click Reset ().
 

Goal: Identify a limiting reactant.
Count: H2O is the chemical formula for water. In order to produce a single molecule of water, how many hydrogen atoms are needed? _______  Oxygen atoms? _______
Predict: Set the number of O2 molecules to five and the number of H2 molecules to eight.
How many oxygen atoms are present? ___Hydrogen atoms? _______
How many water molecules could form from these reactants? _______
After the molecules react, which reactant will be left over? _______ ______
Which reactant will be the limiting reactant? ___________ ____
Click Play and wait until Reaction complete is shown. What happened? _________ _____________ _____________________________
Test: Click Reset.Set the number of O2 molecules to 10.
How many hydrogen molecules (H2) will be needed for there to be no excess reactants? ______ Use the slider to set the number of H2 molecules to this value.
How many water molecules will be formed? _______
Click Play. What happened?
Challenge yourself: Run the Gizmo with five O2 molecules and nine H2 molecule
How many of each molecule do you think will be produced by this reaction?
O2: _______                   H2: _______                           H2O: _______
Click Play. How many were actually produced? O2: _____ H2: _____ H2O: ____
How do you explain this result? _______ ___
Activity B:

Methane reaction
Get the Gizmo ready:
  • Select C + H2 becomes CH4.
 
Goal: Predict the results of a chemical reaction.
Count: CH4 is the chemical formula for methane. In order to produce a single molecule of methane, how many carbon (C) atoms are needed? _______ Hydrogen atoms? _______
Predict: Set the number of C atoms to 14 and the number of H2 molecules to 10.
How many total hydrogen atoms are there? _______
How many methane molecules could form from these reactants? _______
After the atoms react, which reactant will be left over? ________
Which reactant will be the limiting reactant? __ _____________
Click Play and wait until Reaction complete is shown. What happened?
Test: Click Reset.Set the number of C atoms to seven.
How many hydrogen molecules (H2) will be needed for there to be no excess reactants? _____ Use the slider to set the number of H2 molecules to this value.
How many methane molecules will be formed? _______
Click Play. What happened?.
Solve: For each chemical equation below, write the number of product molecules that will form from the reaction. Then, circle the limiting reactant. (Note: The coefficients in front of the reactants indicate the number of reactant molecules or atoms present.)
5C + 6O2 à _______ CO2
4Na + 8Cl2 à ___NaCl
3CO2 + 4H2O à _______ H2CO3
7N2 + 9H2 à _______ NH3
10Zn + 16HCl à _______ ZnCl2 + _______ H2

Comments

  1. UnknownMay 16, 2020 at 1:49 PM

    This is not an answer key there aren't any answers

    ReplyDelete

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