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Unit # 2.1 Types of Chemical Reactions and stoichiometry

Unit # 2.1 Types of Chemical Reactions and stoichiometry . A closer look at aqueous Reactions. Essential Understandings . Defining and utilizing different types of chemical reaction equations Molecular Equations Complete Ionic Equations Net-Ionic Equations

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Unit # 2.1 Types of Chemical Reactions and stoichiometry

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  1. Unit # 2.1Types of Chemical Reactions and stoichiometry A closer look at aqueous Reactions

  2. Essential Understandings • Defining and utilizing different types of chemical reaction equations • Molecular Equations • Complete Ionic Equations • Net-Ionic Equations • Metathesis Reactions (Double Exchange) • Predicting Products for this type of reaction • How to use Solubility Rules for determining if a precipitate will form in a metathesis reaction • Continue to work with Acid/Base Reactions • Solving more complex stoichiometry problems

  3. Moving Past Molecular equations Types of reaction equations

  4. Molecular Equations • Write a complete reaction equation for the reaction: • Aqueous silver nitrate reacts with aqueous potassium chloride to yield solid silver chloride and aqueous potassium nitrate. • This is an example of a molecular equation, all reactants and products are written as if they were molecular in nature or found as complete compounds.

  5. Complete Ionic Equations • We can breakdown the previous equation into its ionic parts. If the aqueous compound is a strong electrolyte it can be written as individual cations and anions. • How can we tell if the compounds are strong electrolytes? • We need to look for soluble ionic compounds or strong acids. • Important: Only aqueous reactants or products can be separated into ions. Solids, Liquids, and Gases will not appear as ions. Weak electrolytes will not appear as ions either. • A complete ionic equation is: a reaction equation that shows all the ions present in the reaction

  6. Complete ionic equations • Translate the reaction into a complete ionic equation: • Aqueous silver nitrate reacts with aqueous potassium chloride to yield solid silver chloride and aqueous potassium nitrate.

  7. Net-ionic equations • If we analyze the complete ionic equation we just wrote, what do we see about some of our ions? • Some ions appear on both side of the equation. They are unchanged in the reaction process. • These ions are known as Spectator Ions: Ions that appear in identical forms among both reactants and products of a complete ionic equation. • By eliminating spectator ions from a reaction equation we can produce a Net-Ionic Equation.

  8. Net-ionic equations • Let’s rewrite our complete ionic equation again: • Now cross out each spectator ion from both sides of the equation. • Rewrite the equation without the spectator ions, thus producing a net-ionic equation:

  9. Net-ionic equations • The purpose of a net-ionic equation is to show what ions are actually involved in the reaction. • We are only concerned with what is chemically changed in the reaction. The rest is unimportant information.

  10. Net-ionic equations • Two additional points about Net-ionic equations: • If a reaction equation contains all spectator ions on both sides of the equation, then no reaction actually takes place. • Multiple reactions can lead to the same Net-ionic reaction equation.

  11. Practice Problems • Aqueous lead (II) nitrate reacts with aqueous potassium iodide to yield solid lead (II) iodide and aqueous potassium nitrate. • Write a balanced molecular equation for this reaction. • Write a complete ionic equation • Write a net-ionic equation

  12. Practice Problems • Aqueous barium chloride reacts with aqueous potassium sulfate to yield solid barium sulfate and aqueous potassium chloride. • Write a balanced molecular equation for this reaction. • Write a complete ionic equation • Write a net-ionic equation

  13. Practice Problems • Aqueous nitric acid is neutralized by a potassium hydroxide solution • Perchloric Acid is neutralized by aqueous lithium hydroxide • For each reaction write: • A balanced molecular equation • A complete ionic equation • A net-ionic equation

  14. Also know as double replacement reactions Metathesis Reactions

  15. Metathesis comes from a Greek word that means “to transpose” AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Metathesis (Exchange) Reactions

  16. Metathesis comes from a Greek word that means “to transpose” It appears the ions in the reactant compounds exchange, or transpose, ions AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Metathesis (Exchange) Reactions

  17. Metathesis comes from a Greek word that means “to transpose” It appears the ions in the reactant compounds exchange, or transpose, ions AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq) Metathesis (Exchange) Reactions

  18. Metathesis Reactions • What is the name for the solid product that is produced when two aqueous solutions of ionic compounds are mixed? • It is known as a precipitate • The key to any metathesis reaction is to determine if one of the “exchange” products is insoluble or produces a gas • If so, a reaction takes place • If not, no reaction takes place • Solubility rules will help determine if a precipitate is produced.

  19. Solubility rules How to determine if a reaction will produce a solid product

  20. Solubility rules • This chart provides a guideline for determining if a proposed compound would be soluble in water. • This chart will not have to be memorized, but you will need to be efficient with it. • Lets look for trends in the Solubility Rules:

  21. Practice Problem • Classify the following ionic compounds as soluble or insoluble in water: (write the formula, consult the solubility rules, determine if its soluble or not) • sodium carbonate • lead sulfate • cobalt (II) hydroxide • barium nitrate • ammonium phosphate

  22. Metathesis Reactions and Solubility • Example Problems: • Determine if the two given aqueous solutions will result in a precipitation reaction, or in no reaction. If they are a precipitate reaction, determine the net-ionic equation for the reaction. • Calcium chloride and sodium carbonate • Silver acetate and zinc nitrate • Ammonium hydroxide and calcium bromide • Potassium sulfate and mercury (II) nitrate

  23. Gas Forming Reactions • A second type of double exchange reaction is one that leads to the formation of a gas. • These reactions are somewhat unique since some undergo a secondary reaction that produces reaction products that would not be expected.

  24. Gas Forming Reactions • We have already looked at three examples of gas forming reactions • They involve: • Carbonates • Bicarbonates • Sulfides • Reacting with an Acid • The only other example we will have to consider are reactions that involve sulfites (compounds with SO32-) and acids

  25. Examples of reactions that fit into this category of reactions: CaCO3 (s) + HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l) NaHCO3 (aq) + HBr(aq) NaBr(aq)+ CO2 (g) + H2O (l) SrSO3 (s) + 2 HI(aq) SrI2 (aq) + SO2 (g) + H2O (l) Na2S (aq) + H2SO4 (aq) Na2SO4 (aq) + H2S (g) Translate each of the above reactions into Net Ionic Equations Gas-Forming Reactions

  26. Assignment • Read section 4.2 and take notes as necessary. • Complete the following problems at the end of the chapter: • 20, 21, 23, 24, 25, 27

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