Limiting Reactants Gizmo Answer Key

Name: Osvaldo Zavala Date: 06-08-2022 Student Exploration: Limiting Reactants Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. 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. 1. How many total hot dogs can you make? 30 2. Which ingredient limited the number of hot dogs you could make? Buns 3. Which ingredient will you have leftovers of? Weiners 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. 1. Use the sliders to set the number of O2 molecules and H2 molecules to two. A. How many hydrogen molecules (H2) are there? 2 Hydrogen atoms? 4 B. How many oxygen molecules (O2) are there? 2 Oxygen atoms? 4 2. How many H2O molecules do you think will form when these four molecules react? 2 molecules 3. Click Play ( 2 molecules ). 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 1. Count: H2O is the chemical formula for water. In order to produce a single molecule of water, how many hydrogen atoms are needed? 2 hydrogen atoms 1 oxygen atom Oxygen atoms? 2. Predict: Set the number of O2 molecules to five and the number of H2 molecules to eight. A. How many oxygen atoms are present? 10 atoms 8 molecules B. How many water molecules could form from these reactants? C. After the molecules react, which reactant will be left over? D. Which reactant will be the limiting reactant? 16 atoms Hydrogen atoms? 8 Oxygen E. Click Play and wait until Reaction complete is shown. What happened? Due to the hydrogen and oxygen reacting, there are eight water molecules and one remaining oxygen molecule. 3. 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? 20 hydrogen molecules Use the slider to set the number of H2 molecules to this value. B. How many water molecules will be formed? 20 C. Click Play. What happened? 20 water molecules were formuled 4. 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? O2: 4 used 1 left H2: 8 used 1 left H2O: B. Click Play. How many were actually produced? O2: 4 use d1 H2: 8 8 use d1 H2O: 8 left left C. How do you explain this result? This is the outcome because it takes 10 hydrogen molecules to create the same amount of oxygen that we have, but we only have 9. This is because 2 molecules of hydrogen gas produce 1 molecule of oxygen gas. That's why it only requires 8 hydrogen atoms to create 4 oxygen atoms. This explains why there is only one remaining molecule for each component. There are 8 water molecules since each hydrogen molecule makes one water molecule. Activity B: Get the Gizmo ready: ● Select C + H2 becomes CH4. Methane reaction Goal: Predict the results of a chemical 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? 1 Hydrogen atoms? 4 2. 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? 20 B. How many methane molecules could form from these reactants? C. After the atoms react, which reactant will be left over? D. Which reactant will be the limiting reactant? 5 The carbon Hydrogen E. Click Play and wait until Reaction complete is shown. What happened? Each hydrogen molecule formed a connection with carbon (4 hydrogen molecules percarbon). There are extra carbon atoms that did not link because there are additional carbon atoms. 3. 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? 14 Use the slider to set the number of H2 molecules to this value. B. How many methane molecules will be formed? 7 C. Click Play. What happened? Since all of the hydrogen molecules linked to the carbon, there were no extra reactants. 4. 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 + 6O2 🡪 B. 4Na + 8Cl2 🡪 5 4 CO2 NaCl C. 3CO2 + 4H2O 🡪 D. 7N2 + 9H2 🡪 E. 10Zn + 16HCl 🡪 3 6 8 H2CO3 NH3 ZnCl2 + 8 H2