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Chapter 8 (cont.) TYPES OF REACTIONS- patterns observed empirically allow prediction of products when reactants are known
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SYNTHESIS More complex product made from simpler substances General format : A + X → AX element + element → compound EX: Sodium + chlorine → Magnesium + nitrogen → Sodium + oxygen →
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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 →
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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) + CuCl 2 → OR: Y + BX → BY + X Ex: Cl 2 + NaBr →
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Examples: iron is added to a solution of silver nitrate (assume Fe 3+ ) A piece of sodium is dropped into water Fluorine is bubbled into a solution of potassium iodide
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Single Replacement (cont.) More active 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 active nonmetals gain electrons (get reduced) more easily & form negative ions Reactions where e - ’s are transferred can be classified as oxidation-reduction or redox reactions.
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DOUBLE REPLACEMENT REACTIONS “IONS SWITCH PARTNERS” AX + BY → AY + BX Cmpd + cmpd → two different compounds 1.Precipitation Rxns a)One product is soluble, the other is not b)Use solubility rules to determine if there is a precipitate EX: NaCl (aq) + AgCH 3 COO (aq) →
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1. Precipitation Rxns (cont) Ex: Solutions of barium nitrate and sodium sulfate are combined: Solutions of lithium sulfate and magnesium bromide are combined.
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2. Acid/Base Neutralization Acid + base → salt + water (H + )(OH - ) nitric acid + lithium hydroxide → sulfuric acid + potassium hydroxide → Acetic acid + barium hydroxide →
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Net Ionic Equations 1.Formula Unit Equation- normal balanced equation including states (NH 4 ) 2 S (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
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Combustion Reactions Hydrocarbon + oxygen → carbon dioxide + water C x H y + O 2 → CO 2 + H 2 O Ex: Liquid decane, C 10 H 22, is burnt in air
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Ammonium dichromate (Cr 2 O 7 2- ) decomposes with heating into chromium (III) oxide, nitrogen, and water vapor. White phosphorus (P 4 ) ignites spontaneously in air to form solid tetraphosphorus decaoxide.
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Ammonium nitrate is used as a fertilizer even though it can be explosive. It can be made by bubbling ammonia gas (NH 3 ) 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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