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Understanding Types of Chemical Reactions and Their Predictions

Chapter 8 focuses on the various types of chemical reactions observed empirically. It covers synthesis, decomposition, single replacement, double replacement, and combustion reactions. Synthesis involves creating complex products from simpler substances, while decomposition breaks compounds down into simpler parts. Single replacement reactions involve a more active element displacing another, and double replacement reactions involve ions switching partners. Finally, combustion reactions result in carbon dioxide and water. The chapter emphasizes the importance of understanding these reactions for predicting products from known reactants.

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Understanding Types of Chemical Reactions and Their Predictions

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  1. Chapter 8 (cont.) TYPES OF REACTIONS- patterns observed empirically allow prediction of products when reactants are known

  2. SYNTHESIS • More complex product made from simpler substances • General format : A + X → AX element + element → compound • EX: • Sodium + chlorine → • Magnesium + nitrogen → • Sodium + oxygen →

  3. DECOMPOSITION • A single reactant is broken down into simpler substances • AX → A + X • CMPD → ELEMENT + ELEMENT Most require an input of energy to break the bonds in the reactants. • EX: water → • magnesium bromide →

  4. SINGLE REPLACEMENT REACTIONS • An element on its own pushes another SIMILAR element out of a cmpd (replaces it) • An element can only be replaced by a more active element. Check activity series to decide if rxn will occur. • A + BX → AX + B element + cmpd → different cmpd + diff. elem. Ex: Al (s) + CuCl2 → OR: Y + BX → BY + X Ex: Cl2 + NaBr →

  5. Examples: • iron is added to a solution of silver nitrate (assume Fe3+) • A piece of sodium is dropped into water • Fluorine is bubbled into a solution of potassium iodide

  6. Single Replacement (cont.) • Moreactive metals get oxidized (give up electrons more easily to form positive ions), • less active metals will accept them-get reduced • LEO GER • Atoms of uncombined elements have 0 oxidation number. • More activenonmetals gain electrons (get reduced) more easily & form negative ions • Reactions where e-’s are transferred can be classified as oxidation-reduction or redox reactions.

  7. DOUBLE REPLACEMENT REACTIONS • “IONS SWITCH PARTNERS” • AX + BY → AY + BX Cmpd + cmpd → two different compounds • Precipitation Rxns • One product is soluble, the other is not • Use solubility rules to determine if there is a precipitate EX: NaCl (aq) + AgCH3COO (aq) →

  8. 1. Precipitation Rxns (cont) • Ex: Solutions of barium nitrate and sodium sulfate are combined: • Solutions of lithium sulfate and magnesium bromide are combined.

  9. 2. Acid/Base Neutralization • Acid + base → salt + water (H+) (OH-) • nitric acid + lithium hydroxide → • sulfuric acid + potassium hydroxide → • Acetic acid + barium hydroxide →

  10. Net Ionic Equations • Formula Unit Equation- normal balanced equation including states (NH4)2S(aq) + Cd(NO 3)2 (aq) → 2. Total Ionic Equation – all aqueous substances are separated into ions. Note: polyatomic ions stay together as a group. Cancel all spectator ions 3. Net ionic equation- rewrite remaining equation w/states

  11. Combustion Reactions • Hydrocarbon + oxygen → carbon dioxide + water CxHy + O2→ CO2 + H2O Ex: Liquid decane, C10H22 , is burnt in air

  12. Ammonium dichromate (Cr2O72-) decomposes with heating into chromium (III) oxide, nitrogen, and water vapor. • White phosphorus (P4) ignites spontaneously in air to form solid tetraphosphorus decaoxide.

  13. Ammonium nitrate is used as a fertilizer even though it can be explosive. It can be made by bubbling ammonia gas (NH3) through a solution of nitric acid. • An electric current is passed through a sodium chloride solution and forms sodium hydroxide, chlorine and hydrogen. The water in the solution participates in the reaction.

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