Student Exploration: Limiting Reactants

Name: Date: 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 hot dogs 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? Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved 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 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 molecules oxygen hydrogen E.​ Click Play and wait until Reaction complete is shown. What happened? There are 8 water molecules, due to the hydrogen and oxygen reactant and one oxygen molecule left over. 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 B.​ How many water molecules will be formed? 20 C.​ Click Play. What happened? 20 molecules formed 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 B.​ Click Play. How many were actually produced? O2: 1 H2O: H2: 8 1 H2O: 8 C.​ How do you explain this result? The reaction needs 2 hydrogen molecules to make 1 oxygen molecule. To use all the oxygen, 10 hydrogen molecules would be required, there’s only 9. So only 8 hydrogen Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved​ ​ molecules react, which makes 4 oxygen molecules react. That leaves 1 hydrogen molecule and 1 oxygen molecule unused. Since each hydrogen molecule forms one water molecule, 8 water molecules are produced. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved