Honors Chemistry s7

Honors Chemistry

Predicting Reactions

There are several reaction types to know. We will be focusing on the following reaction types

·  Synthesis

·  Decomposition

·  Single replacement

·  Double replacement

·  Combustion

Use the following examples to complete practice problems.

COMBINATION/SYNTHESIS: (SOME REDOX)

1.  Two elements → binary compound

metal + nonmetal → salt (ionic – transfer)

nonmetal + nonmetal → molecule (covalent – share)

(except two metals → no reaction)

Ex) 2Na(s) + Cl2(g) → 2NaCl(s)

Ex) S(g) + O2(g) → SO3(g)

2.  Nonmetal oxide + water → oxyacid

Ex) H2O(l) + CO2 (g) → H2CO3(aq)

Ex) H2O(l) + SO2 (g) → H2SO3(aq)

3.  Active metal oxide + water → metal hydroxide (Group I & II metals only )

Ex) K2O(s) + H2O(l) → 2KOH(aq)

4.  Metal + oxygen → metal oxide

Ex) Zn(s) + O2(g) → ZnO(s)

5.  Ammonia + acid → ammonium salt

Ex) NH3 (aq)+ HCl(aq) → NH4Cl (aq)

DECOMPOSITION: (SOME REDOX)

1.  Metallic carbonates (heated) → metal oxide + carbon dioxide

Ex) CaCO3(s) CaO(s) + CO2(g)

2.  Metallic bicarbonates (heated) → metal carbonate + carbon dioxide + water

Ex) 2NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g)

3.  Metallic hydroxide (heated) → metal oxide + water

Ex) Mg(OH)2(s) MgO(s) + H2O(l)

4.  Metallic chlorates (heated) → metal chloride + oxygen

Ex) 2KClO3 (s) 2KCl(s) + 3O2(g)

5.  Oxyacid (heated) → nonmetal oxide + water

Ex) H2CO3 CO2(g) + H2O(l)

6.  Binary compound (heated or electrolyzed) → constituent elements

Ex) 2HgO(s) 2Hg(s) + O2(g)

Ex) 2H2O(s) 2H2(g) + O2(g)

SINGLE REPLACEMENT: (REDOX)

1.  Replacement of a metal in a compound by a more active metal

metal + aqueous salt → new metal + new salt

Ex) Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)

2.  Active metal + water → metal hydroxide + hydrogen

Ex) Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

3.  Metal + acid → salt (dissolved) + hydrogen gas (bubbles)

Ex) Al(s) + H2SO4 (aq) → Al2(SO4)3(aq) + H2(g)

4.  Replacement of a halogen by a more active halogen (*Order on P.T.)

Halogen + aqueous halide salt → new halogen + new halide salt

Ex) Cl2 (g)+ KBr(aq) → KCl(aq) + Br2(l)

METATHESIS (DOUBLE REPLACEMENT)

These reactions begin with two reactant compounds and produce two product compounds. They typically occur when the reactants are acids, bases or salts. The two major classes are metathesis and acid/base reactions.

1.  2 aqueous salts → 2 new salts

Ex) AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

2.  Acid + base (metal hydroxide) → salt + water (neutralization)

Ex) H2SO4 (aq)+ Ca(OH)2(aq) → CaSO4(aq) + H2O(l)

Ex) HC2H3O2(aq) + Al(OH)3(s) → Al(C2H3O2)3(aq) + H2O(l)

3.  Acid + salt → new acid + new salt

Ex) HCl(aq) + NaC2H3O2(aq) → NaCl(aq) + HC2H3O2(aq)

Gas Production Double Replacement Reactions: formation of a precipitate and neutralization are both driving forces in a reaction. But the formation of a gas or a weak acid is also a driving force. If a gas or a weak acid can be produced in a double replacement reaction, then it will. You already know your weak acids and some of the more commonly produced gases are:

Common gases:

·  H2S

·  CO2 This is often predicted as the product H2CO3 but in reality this is CO2 and H2O

·  SO2 This is often predicted as the product H2SO3 but in reality this is SO2 and H2O

·  NH3 This is often predicted as the product NH4OH but in reality this is NH3 and H2O

4.  Acid + metal carbonate (or bicarbonate) → salt + water + carbon dioxide gas

Ex) HCl(aq) + Na2CO3(aq) → NaCl(aq) + H2O(l) + CO2(g)

5.  Acid + sulfide salt → salt + hydrogen sulfide gas

Ex) HCl(aq) + K2S(aq) → KCl(aq) + H2S(g)

6.  Ammonium salt + metal hydroxide → ammonia gas + salt + water

Ex) NH4Cl(aq) + NaOH(aq) → NH3(g) + NaCl(aq) + H2O(l)

COMPLETE COMBUSTION with Oxygen (REDOX)

1.  Hydrocarbon + oxygen gas → carbon dioxide + water

Ex) CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l)