1 / 24

Introduction to:

Introduction to:. Balancing Chemical Equations. Outline. Information in Chemical Equations Why do we have to balance equations?? Human Balancing Act Balancing Chemical Equations - Easy as 1,2,3...4! Practice makes perfect or something along those lines. BIG IDEA of Unit.

zeus-hampton
Download Presentation

Introduction to:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction to: • Balancing Chemical Equations

  2. Outline • Information in Chemical Equations • Why do we have to balance equations?? • Human Balancing Act • Balancing Chemical Equations - Easy as 1,2,3...4! • Practice makes perfect or something along those lines...

  3. BIG IDEA of Unit • Chemicals react with each other in predictable ways!

  4. Chocolate Chip Oatmeal Cookies • Turn on oven to 170 degrees C • Place first 5 ingredients in mixing bowl, mixing well after each addition • In cup, dissolve baking soda and hot water, then add in mixing bowl • Add flour, oats, & chocolate chips. Mix well • Drop in spoonfuls onto cookie sheets • Bake in oven until starting to turn golden. • Makes about 50 cookies • Ingredients: • 1 cup butter at room temperature • 1 1/2 cups brown sugar • 1 teaspoon vanilla essence • 1/2 teaspoon baking soda • 1 tablespoon hot water • 1 1/2 cups unbleached flour • 1 1/2 cups rolled oats • 1 1/2 cups chocolate chops

  5. Balanced Chemical Equation • 2 H2(g) + O2(g) → 2H2O (g)

  6. Comparison

  7. Recall (from earlier this class!): • Law of conservation of mass • In a given chemical equation, the mass of the reactants is equal to the mass of the products • Chemical equations obey this law - show all the atoms of the reactants are still present in the products • Coefficients are added before chemical formulas in an equation to ensure that the number of atoms on each side of the arrow are equal (balanced!)

  8. Human Balancing Act 1 • Word equation: sodium + chlorine → sodium chloride • What are the chemical formulas of the reactants and product in this equation?

  9. Human Balancing Act 1 • Na + Cl2 → NaCl • Volunteers needed to balance this equation!

  10. Human Balancing Act 1 • Balanced Equation: 2Na + Cl2 → 2NaCl

  11. Human Balancing Act 2 • A little trickier! • Word equation: zinc + silver nitrate → zinc nitrate + silver • What are the chemical formulas of the reactants and products in this equation??

  12. Human Balancing Act 2 • Zn + AgNO3 → ZnNO3 + Ag • Volunteers to balance equation! • Hint: Because polyatomic ions generally stay intact, you can count them the same way as you count atoms!

  13. Human Balancing Act • Balanced Equation: Zn + 2AgNO3 → Zn(NO3)2 +2Ag

  14. Steps for Balancing Chemical Equations: • EXAMPLE: Write the balanced chemical reaction of magnesium with oxygen. • STEP 1:Write word equation for the reaction • Eg. magnesium + oxygen → magnesium oxide

  15. Steps for Balancing (Continued) • STEP 2: Replace each chemical name with the correct chemical formula. (This is called the skeleton equation) • Eg. Mg + O2 → MgO

  16. Steps for Balancing (Continued) • STEP 3: Count the number of atoms of each type on either side of the arrow. • Eg. Mg + O2 → MgO • 1 Mg atom 1 Mg atom • 2 O atoms 1 O atom

  17. Steps for Balancing (Continued) • STEP 4: Multiply the formulas by an appropriate coefficient until all the atoms are balanced. Keep checking whether the numbers of each type of atom on both sides are balanced. • Eg. MgO (on right) must be multiplied by coefficient 2 to balance oxygen atoms • Mg + O2 →2MgO • Mg (on left) must be multiplied by coefficient 2 so there are two Mg atoms on each side • 2Mg + O2 → 2MgO

  18. Balanced Chemical Equation • The final balanced chemical equation is: • 2Mg + O2 → 2MgO

  19. Something a little more complicated... • Write a balanced chemical equation for the reaction between iron (111) nitrate and sodium hydroxide to produce iron (111) hydroxide and sodium nitrate.

  20. Step-by-Step • STEP 1: iron (111) nitrate + sodium hydroxide → iron (111) hydroxide + sodium nitrate • STEP 2: Fe(NO3)3 + NaOH → Fe(OH)3 + NaNO3 • STEP 3: • Reactants: • 1 Fe atom, 3 NO3 -ions, 1 Na atom, 1 OH - ions • Products: • 1 Fe atom, 1 NO3-ion, 1 Na atom, 3 OH - ions

  21. Ta-da! • STEP 4: Multiply NaOH (reactants) by 3 and NaNO3 (products) by 3 to get final balanced equation • Fe(NO3 ) + 3NaOH → Fe(OH)3 + 3NaOH

  22. Remember... Or at least the key to chemical equations...

  23. Balancing Chemical Equations Summary: • STEP 1: The word equation • STEP 2: The skeleton equation • STEP 3: Count atoms and ions on reactants and products side. Add coefficients! • STEP 4: The balanced equation! • For more assistance, consult pages 233-236 in text!

  24. Time to Practice! • Worksheet on balancing chemical equations!

More Related