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Chapter 4.1 & 5.3. SYNTHESIS AND DECOMPOSITION REACTIONS ELEMENTS AND THEIR OXIDES. Another good one:. http://www.funnyjunk.com/channel/Chemistry+Jokes+are+fun/cpmqGpc. Predicting Chemical Reactions.
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Chapter 4.1 & 5.3 SYNTHESIS AND DECOMPOSITION REACTIONS ELEMENTS AND THEIR OXIDES
Another good one: http://www.funnyjunk.com/channel/Chemistry+Jokes+are+fun/cpmqGpc
Predicting Chemical Reactions • Using the periodic table, we can figure out the properties of the elements Ex. H, N, O, F, Cl, Br, I elements are all diatomic • Since the properties of the elements are predictable, the chemical reactions they undergo are also predictable Ex. Na and K are both alkali metals that react with Cl to form very stable compounds
Synthesis Reactions • Two reactants combine to make a larger, more complex product Synthesis reaction between sodium and chlorine: http://www.youtube.com/watch?v=Mx5JJWI2aaw
Synthesis of Ionic Compounds • Metal + Non-Metal Ionic Compound Ex. 2 K(s) + Cl2 (g) 2 KCl (s) REMEMBER: Always apply the criss cross rule when making ionic compounds!
Synthesis of Molecular Compounds • Non-metal + Non-metal Molecular compound • Can involve: • HYDROGEN: Easy to predict because H usually forms molecular compounds and follows general pattern of synthesis Ex. H2 (g) + F2 (g) HF (g) • NO HYDROGEN: difficult to predict because the reaction depends on reaction conditions. Ex. C and O can make CO or CO2 depending on the amount of oxygen available to react
Oxides– A Special Type of Synthesis • Oxide: a compound made up of any element and oxygen • Basic oxidesMg + O2 MgOMgO + H2O Mg(OH)2 • Acidic oxidesCO2 (g) + H2O (l) H2CO3 (aq)SO3 (g) + H2O (l) H2SO4 (aq) NO2(g) + H2O (l) HNO3 (aq) + HNO2 (aq)
Recall: • pH < 7 = acidic solution, pH= 7 neutral solution, pH > 7= basic solution • Acids produce H+ ions in solution • Bases produce OH- ions in solution
Decomposition Reactions • A compound breaks down to form two or more simpler products • Generally need energy (heat, catalyst, electricity) to get started
Decomposition of Ionic Compounds • Ionic compound Element + Element Ex. 2 KCl (l) 2 K (s) + Cl2 (g) This reaction involves passing electricity through KCl to break it down into its elements K and Cl
Decomposition Involving Compounds • Compounds with polyatomic ions or molecular compounds are difficult to predict • Use chemical tests to detect what the products are (often testing for presence of gas)Ex. 2 KClO32 KCl + 3 O2 Ex. CaCO3 CaO + CO2 Note: Both reactions require heat
Examples Identify the reaction type: • 2 HCl H2 + Cl2 • Cl2O (g) + H2O (l) 2 HClO (aq) • 2 AlCl3(s) 2 Al (s) + 3 Cl2 (g) • KO(g) + H2O (l) 2 KOH (aq)
Some Helpful Links • Synthesis and decomposition reactions explained:http://www.youtube.com/watch?v=yS8noHTIJ_E • Basic and acidic oxides:http://www.youtube.com/watch?v=MtL64hRoTzQ
Homework pg. 161 # 1, 2, 4 pg. 204 #3, 4, 9