Chem 102 Part 2

• Shift in an equilibrium caused by addition of an ion involved in equilibrium
• -addition of common ion decreases solubility of a sparingly soluble salt
• -removal of a common ion increases solubility of a sparingly soluble salt

• Removing CO₃^2- (common ion)
• Increases solubility of CaCO₃

• Rinse buret with 5 mL standardized NaOh
• Buret should be vertical
• Remove funnel from buret
• Read bottom of meniscus to + 0.01 mL
• Eyes should be level with meniscus
• Buret reading card makes bottom of meniscus darker

• Delta G^o = Gibb's free energy
• < 0 reaction is "spontaneous"
• > 0 reaction is "nonspontaneous"
• Delta G^o = -RT ln K
• Delta H^o = Enthalpy
• < 0 reaction is "exothermic"
• > 0 reaction is "endothermic"
• Delta S^o
• > 0 increased disorder
• < 0 decreased disorder
• Delta G^o = Delta H^o - T(delta S^o)

Either as heat and/or work

Part of universe we are focusing on

Everything else around the system

• Sum of kinetic energies and potential energies of all particles in a system
• Typically measure change in internal energy
• delta E = E_final - E_initial = E_products - E_reactants
• If system loses energy (delta E < 0), surroundings gain energy
• If system gains energy (delta E > 0), surroundings lose energy
• -a delta E = 0, means no energy is being transferred

• q = thermal energy (heat) - energy transfer that results only in temperature change
• w = work (mechanical, electrical, etc) = energy transferred when object is moved by force
• eg. reaction that produces a gas
• Delta E < 0 energy lost from system to surroundings
• Delta > 0 energy gained by system from surroundings
• Delta E = q+w = positive + positive = positive
• = negative + negative = negative
• =(positive + negative) = depends

• Law of conservation of energy - total energy of universe is constant
• Delta E = Delta E_system + Delta E_surroundings = 0
• State function - property of system determined by its current state, regardless of the path of that state

Property of system determined by its current state, regardless of the path to that state

Total energy of universe is constant

• Consider only work done by expanding gas
• w = -P(delta V)
• Most reactions performed at constant pressure:
• Delta H = Delta E + P(delta V) at const. P;
• same as q_P = delta E - w
• -change in enthalpy equals the heat gained or lost by system at constant pressure
• Delta H = delta E reactions not involving gases
•           reactions with delta n_GAS = 0
• Delta H ~ Delta E reaction with delta n_GAS not = 0

(Delta H_rxn < 0) = heat lost to surroundings

(Delta H_rxn > 0) = heat gained from surroundings

= heat of formation = heat of reaction for producing 1 mole of product from its elements

= heat of fusion for when 1 mole melts

=heat of vaporization for when 1 mole vaporizes

=heat evoled from dissolving 1 mole of salt into its constituent ions

Science of measuring heats of reaction

• Device used to exp. determine quantity of heat (q) associated with a chem rxn
• -"isolated system" where no energy or matter is exchanged with the surroundings
• -heat of reaction does not escape so must raise temperature of contents of calorimeter

• Calorimetry performed at constant pressure
• quantity of heat = specific heat x mass of substance x delta T
• specific heat x mass of substance = heat capacity

• Are based on dissolution of:
• NH₄NO₃ (s) -> NH₄⁺ + NO₃^- _aq
• Delta H_soln = +25.7 kJ
• Squeezing cold pack bursts a bag of water, allowing water to mix with NH₄NO₃ crystals

• Based on:
• CaO (s) + H₂O (l) -> Ca(OH)₂ (s)
• Delta H = -65.15 kJ

Enthalpy change of an overall process is sum of enthalpy changes of its individual steps

• Standard enthalpy of formation, delta H_f^o = change in enthalpy to form 1 mole of a compound from its elements
• - characteristic of a substance
• elements -> 1 mole of compound
• Standard States - all substances in their standard states
• Gas - pure gas at 1 atm (~1 bar)
• Liquid or solid - pure liquids or pure solid
• Solution - 1 M
• Element - most stable form (g, l, s) at 1 atm and typically 298K
• delta H_f (element) = 0

Property of system determined by its current state, regardless of the path to that state

• Entropy (S) - thermodynamic measure of randomness of disorder
• -as disorder increases, entropy increases
• -natural progression if from order to disorder
• Entropy is closely related to probability
• -spontaneous processes proceed towards states that have highest probability of existing

• Processes occur in direction that increases the entropy of the universe
• delta S_univ = delta S_system + delta S_surroundings

• Thermodynamic measure of randomness or disorder
• Eg. melting ice - crystalline solid is replaced by less structured liquid
• vaporization of water,
• and dissolving NH₄NO₃ in water

• Third law of thermodynamics - perfect crystal has zero entropy at absolute zero (0 K)
• General trends of entropy in a system:
• S (solid) < S (liquid) <<< S (gas)
• -entropy increases when liquids formed from solids
• -entropy really increases when gases formed from solids or liquids
• entropy generally increases as:
• -n_gas increases
• -total volume is increased
• -temperature is increased
• -complexity of a molecule

Perfect crystal has zero entropy at absolute zero (0 K)

Delta G^o_sys = delta H^o_sys - T(delta S^o_sys)

• Delta G < 0, reaction is spontaneous
• Delta G > 0, reaction is non-spontaneous
• reverse rxn is spontaneous
• Delta G = 0, reaction is at equilibrium
• balance between forward & reverse rxns

• [Cu(NH3)6](NO₃)₂ Coordination compound
• [Cu(NH₃] Comlex ion
• (NO₃)₂ Counter Ion
• list cation, then anion
• Metal complex goes in [ ]
• Counter ions outside [ ]
• Hexaminecopper(II) nitrate

• 1. Name cation first then anion
• 2. In naming complex, name ligands before metal. List ligands alphabetically, with anionic ligands ending in -o.  Indicate number of ligands using : di-, tri-, tetra-, penta-, hexa- use bis-, tris-, tetrakis-... for ligands that already have the di-, tri- prefixes (ethylenediamine)
• 3. Count up all anions and look at overall charge to determine oxidation number of metal
• 4. Designate metal oxidation number using Roman numerals (I, II, III, IV...)
• 5. In formula, use [ ] around complex and list metal first, then ligands in alphabetical order.
• Use abbreviations for polydentate ligands. en, ox
• 6. Complex anions: metal ends with -ate (e.g. chromate) exceptions: Fe -> ferrate, Cu -> cuprate (Table 23.9)

• Delta H  Delta S   Delta G      Result
• -             +          -        Always spontaneous
• -            -            -      Low T (spontaneous)
•                           +      High T (non-spon)
• +            +         +     Low T (non-spon)
•                            -    High T (spontaneous)
• +           -           +     Never spontaneous

• when delta G = delta H - T(delta S) = )
• delta H = T(detla S)

Lowering the temperature of a liquid below its freezing point without it becoming a solid

System that is temporarily "trapped" in an excited energy state

• I. Use delta G^o = delta H^o - T(delta S^o)
• possibl to use at many temps
• ii. Use tabulated std free energy of formations (delta G_f^o)
• Summations, m_p = moles of product
• n_r = moles of reactant
• mathematically simpler
• can only use for rxns at 298 K
• iii. delta G^o = -RT ln K

• = relative amounts of reactants or products can drive a reaction
• ie. when not at 1 bar/1M
• Use: delta G = delta G^o + RT ln Q
• Q = Rxn Quotient
• Delta G is driving force of a reaction
• At equilibrium: delta G^o = -RT ln K
• Q<K rxn procees to right: forward reaction delta G < 0
• Q>K forward reaction has delta G >0, and reverse reaction delta G < 0.  Therefore rxn proceeds to the left
• Q=K at equilibrium delta G=0

Another way to determine K or delta G⁰

The flow of electrons. Voltage is the pressure, current is how much flow there is.

The reactions of molecules and atoms with electrons

How readily two reactants will undergo electrochemical reaction

Cell potential is measured in voltage (V)

Standard cell potential.  All reagents 1M or 1 atm at 25⁰C

• Spontaneous chem rxns that generate electric current
• E⁰_cell > 0

• Non-spontaneous rxns, require an electric current to produce chemical change
• E⁰_cell < 0

Fuel cell vehicles, metal refining, metal plating, rust, etc

Movement of electrons from one species to another

Gain of electrons Cu²⁺ to Cu (s)

Loss of electrons Zn (s) to Zn²⁺

Causes another species to be reduced Zn (s)

Cases another species to be oxidized Cu²⁺

• Oxidation Half Rxn
• Zn (s) -> Zn²⁺ (aq) + 2e-

• Reduction Half Rxn
• Cu²⁺ (aq) + 2e- -> Cu(s)

Electricity moves from Anode to Cathode

• Strong oxidizing agent (positive E^o)
• Weak oxidizing agent (negavite E^o)
• Weak reducing agent = strong oxidizing agent
• Strong reducing agent = weak oxidizing agent

= E_cathode - E_anode

Mixture of ions (usually aq) involved in redox rxn or carry charge

• Anode is on left
• Cathode is on right
• Phase boundary is denoted by |
• Half-cell boundary (salt bridge) is denoted by ||
• Ignore non-redox ions in electrolyte
• If half-cell rxn has no solid species to serve as electrode, use inert electrode like Pt or graphite (Exp V)

• E_cell > 0 spontaneous rxn
• Is driving force on e-
• units of volt: 1 V = 1 J/C (amount of energy per unit of charge)
• -potential depends on conc of redox species,

• Amount of work done by a reaction is measured by delta G (J)
• Delta G^o = -RT ln K

• delta G⁰ = -nFE⁰_cell
• delta G⁰ = -RT ln K
• E^o_cell = (RT ln K)/(nF)

• Self contained group of voltaic cells arrganed in series
• Spontaneous electrochemical reaction

• Batteries (voltaic cell) that cannot be recharged
• Primary lithium battery
• Leclache (dry) cell
• Alkaline Battery

• Batteries (voltaic cell that can be recharged
• Lithium ion battery
• Lead Acid Battery (car battery)

• Reactants (combustible fuel and oxygen) flow into battery and products leave cell
• -Use combustion to produce electricity
• Delta E = q + w
• Combustion engine = q + P(delta V)
• Fuel cell = q + w_elec

Electrochemical cell that uses electrical energy to drive a nonspontaneous (E^o < 0, delta G^o > 0) chemical reaction

Listing of reduction half rxns worst reducing agent to best (Scheme B in lab manual)

• Anode: Zn (s) -> Zn²⁺ + 2e-
• Cathode: 2 MnO₂ (s) + H₂O (l) + 2e- _> Mn₂O₃ (s) + 2 OH- (aq)
• Cell: Zn(s) + 2MnO₂(s) + H₂O (l) -> Zn²⁺(aq) + Mn₂O₃ (s) + 2OH- (aq)
• E_cell = 1.55V
• NH₄Cl paste reacts consuming OH- to maintain pH but that generates NH₃ (g).  Build-up of NH₃ (g) minimized by formation of complex ion Zn²⁺ + 2NH₃ (g) + 2Cl- (aq) --> [Zn(NH₃)₂]Cl₂ (s)
• But when current is drawn rapidly from cell, NH₃ builds up near electrode, causing the voltage to drop. Also, acidic electroplyte slowly dissolves Zn (s) electrode
• Acid dissolved Zn²⁺
• Limited shelf life
• Alkaline battery has longer shelf life...
• Cannot recharge because products do not remain in intimate contact with electrodes

• High energy/mass ratio; used in watches and pacemakers
• Anode: 3.5 Li (s) -> 3.5 Li⁺ + 3.5 e-
• Cathode: AgV₂O_5.5(s) + 3.5 Li⁺ + 3.5 e- -> Li_3.5AgV₂O_5.5
• Cell: AgV₂O_5.5(s) + 3.5 Li(s) -> Li_3.5AgV₂O_5.5(s)
• E_cell = 3.5-4.0 V
• Li(s) is highly reactive in water.  Therefore electrolyte must be in an organic solvent.
• Cell can provide power for several years if used at a low rate

• Car battery,
• E_cell =2.02 V
• Recharge is negative, and is possible because PbSO₄ sticks to electrode
• Car battery achieves 12 V by having 6 lead acid batteries in series
• Very low energy/mass ratio - limited use for electric cars

Electrochemical cell that uses electrical energy to drive a nonspontaneous (E^o < 0, delta G^o >0) chemical reaction

• high energy/mass ratio
• Therefore used in laptops, cell phones, etc.
• Li(s) is highly reactive with water, the electrolyte is 1M LiPF₆ in organic solvent

• Reactants (combustible fuel and oxygen) flow into battery and products leave cell
• -use combustion to produce electricity
• PEM = proton exchange membrane
• Electrochem rxn involving gases have large E_a (overvoltage)
• Electro-catalysts (nanoparticle Pt) lower E_a
• delta E = q + w
• Combustion engine = q + P(delta V) 25-40%
• Fuel cell = q + w_elec 75% efficient

• Highly coloured (absorb visible light)
• Paramagnetic (unpaired electrons, interact with magnet)

• Electrons removed from valence-shell s orbital before removed from valence d orbitals
• be able to determin electron configurations for neutrals and ions of d-block elements

• Consist of:
• 1. Metal ion
• -electropositive and a Lewis acid, an electron pair acceptor
• 2. Ligands - molecules and/or anions with lone pairs of e-
• -Lewis bases electron pair donors
• -surround the metal ion
• -bonded to the metal ion
• 3. Counter ions
• -ions not bonded to the central metal atom
• -provide net zero charge for compound

Number of atoms bonded directly to the center metal atom (usually 2, 4, or 6)

• Needed to maintain charge neutrality on the compound
• Tells you total charge on the complex

• 1. Name cation first, then anion
• 2. In naming complex, name ligands before metal. List ligands alphabetically, with anionic ligands ending in -o. Indicate number of ligands using: di-, tri, tetra-, penta-, hexa- use bis-, tris, tetrakis-... for ligands that already have the di-, tri-prefixes (ethylenediamine)
• 3. Count up all anions and look at overall charge to determine oxidation number of metal
• 4. Designate metal oxidation number using Roman numerals (I, II, III, IV...).
• 5. In formula, use [] around complex and list metal first, then ligands in alphabetical order.
• 6. Complex anions: metal ends with -ate (e.g. chromate) exceptions: Fe -> ferrate, Cu-> cuprate (table 23.9)

• Look at the charge on the complex
• Are any of the ligands negatively charged?
• Then calculate the charge (positive) on the metal

• Determine its coordination number (CN)
• Determine metal's d configuration.
• CN = 2, Linear
• CN = 4 Square planar(d⁸) or tetrahedral
• CN = 6, Octahedral

Compounds with same chemical formula but different properties

Atoms connected differently

Ligand and counter-ions swapped (structural isomers)

• Different atom of a monodentate ligand bonded to metal (structural isomers)
• ONO or NO₂

Atoms arranged differently in space relative to central metal atom: cis or trans

• Molecule & mirror image cannot be superimposed
• Chemically identical properties (mirror images)

• Valence bond theory (VBT)
• -assumes covalent bonding
• -explains geometry of complexes
• Crystal field theory (CFT)
• -assumes ionic interactions
• -explains color and magnetism

• metal - Lewis acid - accepts electrons
• ligand - Lewis base - donated electrons
• metal-ligand bond is fully covalent
• equal sharing of e- pair by metal and ligand
• bond formed by overlap f filled ligand orbital and empty metal orbital

Energy required for an electron to enter a partially filled orbital

• linear: metal orbital are sp hybridized
• tetrahedral:metal orbitals are sp³ hybridized
• square planar: metal orbitals are dsp² hybridized
• octahedral: metal orbitals are d²sp³ hybridized
• VBT describes covalent nature of M-L bonds
• VBT does not predict color or magnetic

• CFT does not accurately describe M-L bonding
• CFT predicts colors and magnetic properties
• Metal-ligand bonding is considered fully ionic
• -electrostatic attraction between metal cation (+) and negative ligands
• -either full negative charge
• -or negative dipole
• But are electrons in d-orbitals of metals
• -electrostatic repulsion between d-electrons and negative ligands
• -results in destabilization of all d-orbitals
• -results in splitting of the metal d orbitals

• The delta crystal field splitting depends on:
• 1. Geometry of coord cps
• 2. Oxidation number of metal
• 3. How focused ligand charge is

• Competition between splitting energy and E_pairing
• Low spin = E_pairing<splitting energy
• High spin = E_pairing > splitting energy

• Metals with unpaired electrons
• -affected by magnets
• -more unpaired electrons more affects by magnets

• Metals with all paired electrons
• Unaffected by magnet

• Color can be explained using Crystal Field Theory
• Color caused by absorbance of a photon equal in energy to the difference in orbital energy
• This occurs due to excited states, which normally returns to ground state in 10^-12 seconds
• Sometimes can undergo a reaction
• Sometimes excess energy is emitted as light (fluorescence)-slow process (>10^-9s)

• White light = all colors
• Color observe = colors not absorbed
• Color characterized by wavelength
• E_photon = hv = h (c/wavelength)
• On the color wheel, what you see is opposite of what wavelength they observe

• 1. Different splitting pattern
• 2. Smaller splitting energy - No orbitals directly overlap ligands, splitting energy of tetrahedral < splitting energy of octahedral
• 3. Small splitting energy means tetrahedral complexes always weak-field (high-spin)

• 1. Different splitting pattern
• 2. Total splitting energy for square planar similar to splitting energy of the octahedral

oxygen carrying protein