DAILY QUESTION October 29, What is the general form for synthesis reactions?

Agenda10/29/08 Daily Question Ch 6 Sect 2 Notes Lab Safety Review Assignments: 1. Ch 6 Sect 1 and Sect 2 Review Worksheets due 10/31 2. Extra Credit Crossword Puzzle due Today!

Synthesis Reactions A + B → AB Always join substances to form a new, more complex compound –Water: H + O 2 → H 2 O –Table salt: 2Na + Cl 2 → 2NaCl –Photosynthesis: 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2

Decomposition Reactions AB → A + B Substances are broken down –Electrolysis of water: 2H 2 O → 2H 2 + O 2 –Digestion –“Cracking” oil

Combustion Reactions Use oxygen as a reactant –Water is a common source of oxygen Products depend on the amount of oxygen available –Carbon dioxide –Carbon monoxide –Carbon

Single-displacement Reactions AX + B → BX + A A more reactive element will take the place of a less reactive one –Copper(II) chloride and aluminum 3CuCl 2 + 2Al → 2AlCl 3 + 3Cu Alkali metals react with water to form ions –Potassium and water K + H 2 O → KOH + H 2

Double-displacement Reactions AX + BY → AY + BX Two compounds appear to exchange positive ions –Formation of lead chromate: Pb(NO 3 ) 2 + K 2 CrO 4 → PbCrO 4 + 2KNO 3

Oxidation-Reduction Reactions Reactions where electrons are transferred. Substances that accept electrons are: –Reduced Substances that give up electrons are: –Oxidized In all redox reactions, one reactant is reduced and one is oxidized. They are linked. –Example: Formation of rust

OIL RIG O xidation I s L oss of electrons R eduction I s G ain of electrons

Redox Reactions with Oxygen Don’t have to be with ions… can be oxygen Oxidation: gain of oxygen or loss of hydrogen Reduction: loss of oxygen or gain of hydrogen –Respiration –Combustion

Radicals When a covalent bond is broken and at least one unpaired electron is left on each fragment of the molecule React quickly to form covalent bonds with other substances, making new compounds