* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chap. 4 AQUEOUS RXNS O
Metastable inner-shell molecular state wikipedia , lookup
Artificial photosynthesis wikipedia , lookup
Electron configuration wikipedia , lookup
Biochemistry wikipedia , lookup
Bioorthogonal chemistry wikipedia , lookup
Metallic bonding wikipedia , lookup
Rate equation wikipedia , lookup
Oxidation state wikipedia , lookup
Liquid–liquid extraction wikipedia , lookup
Rutherford backscattering spectrometry wikipedia , lookup
Water splitting wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Marcus theory wikipedia , lookup
Nucleophilic acyl substitution wikipedia , lookup
Click chemistry wikipedia , lookup
Hydrogen-bond catalysis wikipedia , lookup
Acid dissociation constant wikipedia , lookup
Acid strength wikipedia , lookup
Transition state theory wikipedia , lookup
Implicit solvation wikipedia , lookup
Coordination complex wikipedia , lookup
Chemical bond wikipedia , lookup
Hypervalent molecule wikipedia , lookup
Debye–Hückel equation wikipedia , lookup
Chemical reaction wikipedia , lookup
Inorganic chemistry wikipedia , lookup
Stoichiometry wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Electrolysis of water wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Stability constants of complexes wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Acid–base reaction wikipedia , lookup
Electrochemistry wikipedia , lookup
Metalloprotein wikipedia , lookup
Ionic compound wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Chap. 4 AQUEOUS RXNS 4.1 WATER AS A SOLVENT • Describe solution composition in terms of molarity • Water is a polar molecule – “Bent” shape – Covalent bonds – Electrons not shared equally • Describe strong and weak electrolyte solutions, including acids and bases • Use ionic equations to describe neutralization and other metathesis reactions • Determine concentrations by applying solution stoichiometry to titrations IONIC SOLUTE: ELECTROLYTE + _+ + _+ + _+ + _+ nB-(aq) + _+ + _+ + _+ AB(s) → AB(aq) + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + _+ + H • Solution does not conduct electricity • Weak electrolytes: low concentrations of ions ABn(s) → δ+ • Solute dispersed but not dissociated in solution • Solution conducts electricity A+(aq) O • Molecular solute in polar or nonpolar solvent • Solute dissociated to ions in solution STRONG: H NON-IONIC SOLUTE: NONELECTROLYTE • Ionic solute in polar solvent + _+ δ+ – Electrostatic – Dipole • Understand the key event in the redox process Solvated ion δ– • Water overcomes solute particleparticle interactions WEAK: AB(s) ↔ A+(aq) + nB-(aq) NON-IONIC ACID SOLUTE 4.2 AQUEOUS IONIC REACTIONS • Covalent compounds of H • Many reactions of ions involve ionic compounds dissolved (dissociated) in H2O • H—X bonds polar • Solvation by water leads to dissociation • Not all ions participate in reactions • Solvation leads to formation of hydronium ion HX(g) → H+(aq) + X-(aq) H+(ag) + H2O(l) → H3O+(aq) • EXAMPLE: The reaction of sodium hydroxide with hydrogen chloride (hydrochloric acid) – + NaOH(aq) + HCl(g) → NaCl(aq) + H2O MOLECULAR MOLECULAR EQUATION: EQUATION: Reactants Reactants and and products products shown shown as as intact, intact, undissociated undissociated compounds compounds + Page 4-1 4.3 Metathesis (Double Displacement) Reactions: Precipitation Molecular equation does not show what happens: NaOH(s) → Na+(aq) + OH-(aq) HCl(g) → H+(aq) + Cl-(aq) AX + BY → AY + BX Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) → 2NaF + CaCl2 → 2NaCl + CaF2 Na+(aq) + Cl-(aq) + H2O(l) TOTAL TOTAL IONIC IONIC EQUATION EQUATION All All soluble soluble ionic ionic substances substances shown shown as as dissociated dissociated ions ions SPECTATOR SPECTATOR IONS IONS Do Do not not participate participate inin formation formation of of product product H+(aq) + OH-(aq) → H2O(l) Two Two compounds compounds react react and and exchange exchange components components to to form form two two new new compounds compounds NET NET IONIC IONIC EQUATION EQUATION Molecular Molecular equation equation less less spectator spectator ions ions Formation of insoluble product Aqueous media: AX + BY → A+(aq) Y-(aq) B+(aq) X-(aq) AgNO3 soln AgNO3 soln NaHCO3 soln → A+(aq) + Y-(aq) + BX↑↓ NaCl soln NaNO3 soln • Reactants dissociate in solution HCl soln • For reaction to proceed, IONS MUST BE REMOVED FROM SOLUTION: – Formation of an insoluble product (volatile gas or solid precipitate) Na+ + Ag+ + NO3- – Formation of a soluble weak/nonelectrolyte (water) NO REACTION precipitate Na+ + Cl- + H2O + CO2(g) volatile product 4.4 Metathesis Reactions: Table 4.3, p 119 SOLUBLE SOLUBLE Na+ + NO3- + AgCl(s) ANION NO3C2H3O2ClBr- , I2SO SO442- INSOLUBLE INSOLUBLE Acid-Base Reactions COMMENTS COMMENTS All All soluble soluble All All soluble soluble 2+ + 2+ EXCEPT: Hg222+,, Pb Pb2+ EXCEPT: Ag Ag+,, Hg +, Hg 2+ 2+ 2+ EXCEPT: Ag , Hg 2+ + 2 EXCEPT: Ag , Hg2 , Hg2+,, Pb Pb2+ EXCEPT: Ca2+2+, Sr2+2+, Ba2+2+, Ag++, Hg2+2+, Arrhenius Theory : S2PO43OH OH- Anything that produces hydrogen ions when dissolved in water HCl → H+ + Cl- BASE Anything that produces hydroxide ions when dissolved in water NaOH → Na+ + OH- EXCEPT: Ca , Sr , Ba , Ag , Hg , Pb Pb2+ 2+ [X] < 0.01 M CO32- ACID + EXCEPT: EXCEPT: Group Group 1A, 1A, 2A, 2A, NH NH44+ + EXCEPT: EXCEPT: Group Group 1A, 1A, NH NH4 + 4 + EXCEPT: EXCEPT: Group Group 1A, 1A, NH NH44+ 2+ 2+ 2+ EXCEPT: EXCEPT: Group Group 1A, 1A, Ca Ca2+,, Sr Sr2+,, Ba Ba2+ Page 4-2 Complete dissociation in water STRONG HX (X = Cl, Br, I), HNO3, HClO3, ACIDS HClO4, H2SO4 WEAK ACIDS Dissociation STRONG ACIDS AND BASES HCl(g) + H2O(l) → H3O+(aq) + Cl-(aq) NaOH(s) + H2O(i) → Na+(aq) + OH-(aq) Partial dissociation in water HF and most other acids Dissociation in water to yield OHSTRONG Group 1A, 2A metal hydroxides: BASES NaOH, Ca(OH)2 WEAK BASES WEAK ACIDS AND BASES HCN(l) + H2O(l) ↔ H3O+(aq) + CN-(aq) NH3(g) + H2O(l) ↔ NH4+(aq) + OH-(aq) Weak H+ acceptors (from H2O) NH3, C6H5NH2 • Metal hydroxides react with (NEUTRALIZE) acids to produce the salt of the acid and H2O: Acid-Base Titrations HBr + NaOH → NaBr + H2O or H+(aq) + OH–(aq) → H2O(l) Weight Weight FORMULA A A WEIGHT • Weak bases react with acids to produce the salt of the acid: Moles Moles EQUATION Moles Moles A A COEFFICIENT BB SOLUTION MOLARITY NH3 + HCl → NH4Cl Volume Volume Solution Solution AA Not really a net metathesis reaction, by the way: FORMULA WEIGHT Weight Weight BB SOLUTION MOLARITY Volume Volume Solution Solution BB NH3 + H+ → NH4+ Cl– is a spectator ion 4.5 Oxidation-Reduction (Redox) Reactions Titrations V0 Addition of a standard soln of known concentration to a soln of unknown concentration until stoichiometrically equivalent quantities have been reacted (equivalence or end point) Ca(s) + 2H+(aq) → Ca2+(aq) + H2(g) Vf OXIDATION — a reactant loses electron(s) Half-reaction: Ca0 → Ca2+ + 2e- STANDARD SOLN of AX REDUCTION — a reactant gains electron(s) VAX = V0 - Vf Half-reaction: H+ + e- → ½H2 AX + BY → AY + BX MAX × VAX = equivalents of AX added Electrons Electrons are are transferred transferred from from one one reactant reactant to to aa second second reactant reactant Oxidation Oxidation is is always always accompanied accompanied by by reduction reduction VBY Page 4-3 Examples OXIDIZING AGENT • Causes oxidation • Is reduced • Gains electrons (becomes more negative) OXIDATION (LOSE ELECTRONS, become MORE POSITIVE): REDUCING AGENT • Causes reduction • Is oxidized • Loses electrons (becomes more positive) E0 → En+ + ne– Zn → Zn2+ + 2e– Em+ → E(m+n)+ + ne– Fe2+ → Fe3+ + e– En– N3– → ½N2 + 3e– → E0 + ne– REDUCTION (GAIN ELECTRONS, become MORE NEGATIVE): Ca + 2H+ → Ca2+ + H2 E0 + ne– → En– ½O2 + 2e–→ O2– Em+ → E(m–n)+ Fe3+ + e– → Fe2+ → E0 Ag+ + e–→ Ag En+ 2e– + ne– + ne– Oxidation Number Rules Oxidation Numbers (States): Monitoring Electron Transfer 1. For any atom in its elemental form, O.N. = 0 2. For any monatomic ion, O.N. = ionic charge (K+, O.N. = +1; S2–, O.N. = –2) • The charge that an atom (X) in an XY bond would have if its shared electrons were held completely by the atom that attracts the electrons more strongly 3. The O.N. for hydrogen is +1, with the sole exception of metal hydrides (MHn), where O.N. = –1 • The oxidation number (O.N.) of the oxidizing agent DECREASES in a redox reaction 4. The O.N. for oxygen is –2, with the sole exception of peroxides (O22–), where O.N. = –1 • The O.N. of the reducing agent INCREASES in a redox reaction 5. The O.N. for other nonmetals is <0, with the exception of oxyanions, where O.N. > 0 6. The sum of all O.N. in a neutral compound is 0, otherwise ΣO.N. = ion charge Decomposition 4.6 REDOX Reaction Types A → B + C • COMBINATION REACTIONS: Two or more reactants form a single product 2H2O2 → 2H2O + O2 • DECOMPOSITION REACTIONS: A single reactant forms two or more products • DISPLACEMENT (SINGLE REPLACEMENT) REACTIONS: Reactant atoms or ions exchange places O: -1 → 0 O: -1 → -2 Page 4-4 Displacement (Single) Combination A + BX → AX + B A + B → C H2 + CuO → Cu + H2O 2Mg + O2 → 2MgO H: 0 → +1 Cu: +2 → 0 O: 0 → -2 Mg: 0 → +2 Can Can we we predict predict which which elements elements will will displace displace another another element? element? • Nonmetals, particularly halogens, have different strengths as oxidizing agents • Redox reactants can be organized by relative strength in ACTIVITY SERIES, allowing prediction of a reaction’s occurrence Zinc Bromine ½Br2 + e– → Br– Iodine ½I2 + e– → I– Zn → Zn2+ + 2e- • • • Lead Hydrogen Copper Pb → Pb2+ + 2e½H2 → H+ + eCu → Cu2+ + 2e- • • • Gold More easily reduced ½F2 + e- → F– ½Cl2 + e– → Cl– Al → Al3+ + 3e- • • • REDUCTION REACTION Fluorine Li → Li+ + eK → K+ + e- • • • • Redox activity is also reflected in the O.N.s of elements in covalent compounds Chlorine OXIDATION REACTION Lithium Potassium Aluminum – A more active halogen oxidizes a less active halogen More easily oxidized HALOGEN – A more active metal reduces a less active metal METAL Implication for O.N.: Br—Cl +1 –1 Page 4-5 Au → Au3+ + 3e- More easily reduced • In general: • Metals have different strengths as reducing agents More easily oxidized Table 4.14, p 130 Activity Series