Gizmo Limiting Reactants Answer Key

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Gizmo is a learning platform that allows you to learn science and math. Limiting Reactants is one of the science subjects that you will learn on Gizmo. If you want to take the Limiting Reactants test on Gizmo and need the answer to pass the test, then you will be able to find them through this page.

Gizmo Limiting Reactants Answers

Prior Knowledge Questions

Before you use Gizmo, you are able to try these prior knowledge questions.

Imagine you and your friend are making hot dogs. A hot dog consists of a wiener and a bun. At the store, you purchase four packages of eight wieners and three bags of ten buns.

  1. How many total hot dogs can you make?

Answer: 30 hotdogs

  1. Which ingredient limited the number of hot dogs you could make?

Answer: Buns

  1. Which ingredient will you have leftovers of?

Answer: Weiners

Gizmo Warming Up

Just as ingredients can be put together to create a new food, substances can also combine during a chemical reaction to produce new substances. The substances which undergo change are called reactants. And products are the new substances.

Occasionally, 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 on Gizmo, then you are able to determine which reactant is limiting in various scenarios.

To begin, you have to ensure that H2 + O2 becomes H2O. The small 2 in H2, O2 and H2O is a subscript. For your information, subscripts represent the number of atoms in a molecule.

  1. Use the sliders to set the number of O2 Molecules and H2 Molecules to two.

A. How many hydrogen molecules (H2) are there? Hydrogen atoms?

Answer: 2 hydrogen molecules, 4 Hydrogen atoms

B. How many oxygen molecules (O2) are there? Oxygen atoms?

Answer: 2 oxygen molecules (O2), 4 Oxygen atoms

  1. How many H2O molecules do you think will form when these four molecules react?

Answer: 2 molecules

  1. Click Play. How many H2O molecules actually formed?

Answer: 2 molecules

Activity A: Water Reaction

  1. Count: H2O is the chemical formula for water. In order to produce a single molecule of water, how many hydrogen atoms are needed?

Answer: 2 hydrogen atoms and 1 oxygen atom.

  1. Predict: Set the number of O2 Molecules to five and the number of H2 molecules to eight.

A. How many oxygen atoms are present?

Answer: 10 oxygen atoms and 16 hydrogen atoms

B. How many water molecules could form from these reactants?

Answer: 8 molecules

C. After the molecules react, which reactant will be left over?

Answer: 8

D. Which reactant will be the limiting reactant?

Answer: Oxygen

E.  Click Play and wait until Reaction complete is shown. What happened?

Answer: There are eight water molecules, due to the hydrogen and oxygen reactants and one oxygen molecule left over.

  1. Test: Click Reset. Set the number of O2 molecules to 10.

A. 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.

Answer: 20 hydrogen molecules

B. How many water molecules will be formed?

Answer: 20

C. Click Play. What happened?

Answer: 20 water molecules were formed

  1. Challenge yourself: Run the Gizmo with five O2, molecules and nine H2 molecules

A. How many of each molecule do you think will be produced by this reaction?

Answer: O2 4 used 1 left, H2 8 used 1 left, H2O 8

B. Click Play. How many were actually produced?

Answer: O2 4 used 1 left, H2 8 used 1 left, H2O 8

C. How do you explain this result?

Answer: The reason why this is the result is because 2 molecules of hydrogen gas produces 1 oxygen gas, so that means it will take 10 hydrogen molecules to produce the oxygen that we have, but we only have 9 hydrogen. It only uses 8 hydrogen molecules which produce 4 oxygen molecules. This is why there is 1 molecule left for both reactants. Each hydrogen molecule produces one water molecule, which is why there are 8 water molecules.

Activity B: Methane Reaction

  1. 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?

Answer: 1 carbon (C) atoms, 4 Hydrogen atoms

  1. Predict: Set the number of C atoms to 14 and the number of H2 molecules to 10.

A. How many total hydrogen atoms are there?

Answer: 20 hydrogen atoms

B. How many methane molecules could form from these reactants?

Answer: 5 methane molecules

C. After the atoms react, which reactant will be left over?

Answer: The Carbon

D. Which reactant will be the limiting reactant?

Answer: Hydrogen

E. Click Play and wait until Reaction complete is shown. What happened?

Answer: All of the hydrogen molecules bonded with the carbon (4 hydrogen molecules per carbon). Since there are more carbon atoms, there are excess carbon atoms that do not bond.

  1. Test. Click Reset. Set the number of C atoms to seven.

A. 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.

Answer: 14

B. How many methane molecules will be formed?

Answer: 7

C. Click Play. What happened?

Answer: The hydrogen molecules all bonded with the carbon, causing there to be no excess reactants.

  1. 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).

A. 5C + 602

Answer: 5 CO2

B. 4 Na + 8CI2

Answer: 4 NaCI

C. 3CO2 + 4H2O

Answer: 3 H2CO3

D. 7N2 + 9H2

Answer: 6 NH3

E. 10Zn + 16HCI

Answer: 8 ZnCI2 + 8 H2

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