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Unit 6 Chemical Reactions

Unit 6 Chemical Reactions. Objectives. Write chemical equations to describe chemical reactions Balance chemical equations Classify and identify chemical reactions Predict products from chemical reactions. I. Reactions and equations. Chemical reactions: A chemical change has occurred

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Unit 6 Chemical Reactions

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  1. Unit 6 Chemical Reactions

  2. Objectives • Write chemical equations to describe chemical reactions • Balance chemical equations • Classify and identify chemical reactions • Predict products from chemical reactions

  3. I. Reactions and equations • Chemical reactions: • A chemical change has occurred • Evidence of a chemical reaction • Temperature change (energy change) • Change in color

  4. Evidence of chemical change • Gas production (bubbles, fizzing, odor) • Formation of a solid (precipitate)

  5. YouTube - ammonium dichromate volcano • YouTube - Nitrogen Triiodide Detonation • YouTube - Sodium and Water • YouTube - Reaction of Sodium & Chlorine (with subtitles)

  6. Representing chemical reactions: • Reactants: starting substances (written on the left side) • Products: substances that result from the reaction (written on the right side) • Anarrowiswrittenbetweenreactants and products and isread as “yields”

  7. Symbols used in chemical equations (p 203) Pt

  8. Word Equations • Statementsusedtoindicatereactants and products • Lackimportantinformation • Ex.Hydrogen (g) + oxygen (g)  water (l) • Skeletonequations • Chemical formulas are usedtorepresentreactants and products • Ex. H2 (g) + O2 (g)  H2O (l)

  9. Learning Check: • Write the skeleton equations for the following: • Hydrogen (g) + Bromine (l)  hydrogen bromide (g) • Carbon monoxide (g) + oxygen (g)  carbon dioxide (g)

  10. Practice: • Write the skeleton equations for the following: • Hydrogen (g) + Bromine (l)  hydrogen bromide (g) H2 (g) + Br2 (l)  HBr (g) • Carbon monoxide (g) + oxygen (g)  carbon dioxide (g) CO (g) + O2 (g)  CO2 (g) CW p 284 # 3, p 980 9.1 #1,2

  11. II. Balancing chemical equations • Chemical equations: • Must obey “law of conservation of matter” • Must show that the number of atoms of each substance is the same before and after the reaction. • A chemical equation has to be BALANCED • To balance chemical equations, COEFFICIENTS (whole number)are written in front of a reactant or product. • If coefficient is 1, it is not written

  12. Steps for balancing equations • Write the skeleton equation for the reaction. Ex. Hydrogen gas reacts with chlorine gas and yields gaseous hydrogen chloride. H2 (g) + Cl2 (g)  HCl(g) • Count the atoms of each substance for the reactants and products.

  13. Place coefficients (ONLY IN FRONT OF A REACTANT OR PRODUCT) to make number of atoms of each element equal on both sides of the equation. (#atoms= coefficient x subscript) H2 (g) + Cl2 (g)  HCl(g)

  14. Write coefficients in lowest ratio possible H2 (g) + Cl2 (g)  2HCl(g) • Check your answer.

  15. Practice 1. Write a balanced chemical equation if sulfur trioxide when heated yields sulfur dioxide and oxygen.

  16. Write a balanced chemical equation for: Iron (III) oxide iron (II) oxide + oxygen

  17. Balance the following reaction CaO + H2O  Ca(OH)2

  18. Reactions for gummy bear sacrifice KClO3 KCl + O2

  19. CW p balancing equations handout

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