Do Now & Announcements Hand in note packet so I can check your HW (I’ll give it back to you after the quiz) Do Now Quiz (Physical & Chemical Changes) Unit 3 Quest FRI 9/25

Law of Conservation of Matter: Matter cannot be created or destroyed ***This means that you end up with the same number of atoms of each element that you started with.

Example: Consider the reaction of hydrogen gas and oxygen gas (resulting in the production of water) represented by the unbalanced equation below: 2 2 2 1

Consider the modified balanced equation below (there are now 2 Oxygen atoms on the products side by changing the subscript for in H2O to 2, giving us H2O2) While this chemical equation is balanced, explain why it is NOT the same reaction as H2 + O2  H2O?

Balancing Chemical Equations When balancing a chemical equation, you cannot change the subscripts! To balance chemical equations, coefficients can be used to ensure an equal number of atoms are found on both sides of a chemical equation. A coefficient is a number placed in in front of a chemical formula to indicate the number of atoms or molecules.

How can we balance the chemical reaction by adding coefficients? 2 2 2 1 2 1 2 4 4 2 2

Final note: the coefficients represent the relative number of moles of substance that is being reacted or produced. “RECIPE”: 2 1 Think of these questions like reading a recipe How many moles of H2 will react with 1 mole of O2? How many moles of H2O are produced when 1 mole of O2 is reacted? *How many moles of H2 will react with 2 moles of O2? 2 moles 2 moles 4 moles

Balancing Chemical Equations Phet Simulation

Balancing Equations Practice Draw it out if it helps you (examples on next 2 slides) Write in the coefficients for the balanced reaction Identify the reaction type Answer the “moles” question at the bottom

2 1 2 1 Na Cl F Na F Cl Na F Na Cl *What is the total number of moles of NaCl that reacted when 1 mole of Cl2 is produced? _______ 2 moles

1 1 3 3 Fe-O-H Na-Cl Fe-Cl-Cl-Cl Na-O-H O-H Na-Cl Na-O-H Na-Cl Na-O-H *How many moles of NaCl are produced when 1 mole of FeCl3 is completely reacted? 3 moles

Stoichiometry 8 moles NH3 1 mole N2 4 moles N2 2 mole NH3

5.5 mole H2SO4 2 mole NaOH 11 moles NaOH 1 mole H2SO4