Module 5 – Physical chemistry and transition elements

Complex Ion Formation

Complex Ions: Transition metal ion form complex ions. Complex ions formed when ligands bond to central metal ion by coordinate bond.  Ligands: Ligands are molecules or ions that donate lone pair of electrons to a central metal ion to form coordinate bond or dative...

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Complex Ion Shapes

Shape depends on coordination number.  Six Coordinate Complexes: If complex ion has coordination number of 6, gives octahedral shape so 90 bond angles around central metal ion. When MnSO4 is dissolved in water. Forms complex ion with octahedral shape. Learn these...

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Cis- Trans Isomerism in Complex Ions

Stereoisomerism: Complex ions display two types of stereoisomerism: cis- trans isomerism AND optical isomerism.  Cis- Trans Isomerism: Some square planar and octahedral show show cis- trans isomerism. In complex ion, no double bond needed to restrict rotation....

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Optical Isomerism

Optical Isomerism only occurs in octahedral complexes containing two or more bidentate ligands.  Optical isomers aka enantiomers are pair of non- superimposable mirror images of each other.  Cis- isomers may also show optical isomerism such as above.  In questions,...

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Ligand Substitution and Precipitation

Ligand Substitution: A ligand substitution is a reaction in which one ligand in a complex ion is replaced by another ligand.  Reactions of Aqueous Copper (II) Ions: When copper (II) sulphate is dissolved in water, pale blue complex ion formed [Cu(H2O)6] 2+ Ligand...

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pH of Weak Acids

Ka can be calculated from equilibrium amounts.  Approximations: Equation above can be simplified to equation below by assuming two things…  Dissociation of Water: There is a small concentration of H+ from dissociation of water which is neglected. Therefore when HA...

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D Block Elements

D Block Elements: Looking at scandium to zinc of period 4 of d block. All d block are metallic, so high MP, shiny, conduct electricity and heat. The highest energy sub-shell is a d sub-shell.  Electron Configuration: Electrons added to 3d orbitals from 1 to 10....

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pH of Bases

Determine if acid or alkali.  Check if weak or strong before doing method.  Also always check if 2OH or 2H as would be dibasic and would need to multiply conc x 2.  Check in questions if given pKa or Ka.  Kw: Ionic product of water- the ions in water H+ and OH-...

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More Acid and Base Calculations

Addition of 25 cm3 of water to 100 cm3 of 0.100 mol dm-3 Ba(OH)2. Find pH. Dilution question. Given concentration of OH- in original volume but want to find out concentration of OH- in diluted volume. - Concentration x old volume/ new volume = concentration of OH-....

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Buffer Solutions

Buffer Solution: A buffer solution is a system that minimises pH changes when small amounts of acid or base added. Buffer solutions contains 2 things…  Buffer solution contains weak acid, HA, to remove added alkali.  Buffer solutions contain conjugate base, A- ,...

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Buffer Solutions in the Body

Blood Plasma: Blood plasma needs to be at pH 7.4 due to enzymes. pH controlled by buffers such as the carbonic acid- hydrogencarbonate buffer. The body produces more acidic materials than alkaline. Buffers make sure H2CO3 not built up.  Problems with pH: If pH falls...

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Neutralisation

pH Meter: A pH meter consists of an electrode. pH reading displayed. pH meter more accurate than indicator paper, as pH meter does to 2 dp compared to whole number. If data logger attached to pH meter, can plot pH titration curve automatically.  Experiment Monitoring...

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Lattice Enthalpy

Giant Ionic Compounds: Giant ionic compounds have strong ionic bonds- electrostatic attractions between oppositely- charged ions. Must overcome to melt.  Lattice Enthalpy: Lattice enthalpy is the enthalpy change that accompanies formation of one mole of an ionic...

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Factors Affecting Lattice Enthalpy

Factors Affecting Lattice Enthalpy:  Add up ionic radius/ charge if given a range of elements and compounds. When ions in two different groups, need to talk about both ionic charge and ionic size e.g. Mg2+ and Na+.  Don’t write Na, write Na+. Don’t forget the...

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Factors Affecting Hydration Enthalpies

Factors Affecting Hydration Enthalpies: Hydration enthalpies affected by ionic size and ionic charge in same way as lattice enthalpy.  Effect of Ionic Size: Ionic size increase down a group. - MN+ is has a smaller ionic radius than Y+. - Attraction between ion and...

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Redox Reactions

OILRIG: Oxidation is loss of electrons and increase in oxidation number. Reduction is gain of electrons and decrease in oxidation number.  Redox: A reaction where both oxidation and reduction take place.  Oxidation Number: A measure of the number of electrons that...

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Entropy

Entropy: The greater the entropy, the greater the disorder. Units of entropy are JK-1mol-1 . 0K = no energy so minimum disorder.  States of Matter: Generally changing from solids -> liquids -> gas by melting and boiling, increases entropy increase in disorder,...

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Kc

Kc: Remember Kc = products/ reactants. Remember the larger the value, further away from position equilibrium and towards products- AS.  Know how to work out Kc if given equilibrium concentrations. Now looking at how Kc calculated from experimental results.  Kc...

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Free Energy

Feasibility: Reaction can only occur if products have lower overall energy than reactants, then feasible or spontaneous.  Gibbs’ Equation: The overall change during chemical reaction called free energy change- ∆G. Enthalpy change refers to heat transfer between...

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Kp

Kp: Use Kp with gases. Same as Kc but equilibrium constant in terms of partial pressure instead of concentration. Products/ reactants. Balancing numbers is the power. If asked to write Kp expression, no square brackets and remember p… Only include gases, omit other...

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Manganate (VII) Redox Titrations

Redox titrations similar to acid- base titration.  If don’t know which way round colour changes, look at table to see what’s added.  Manganate (VII) Titrations: Potassium manganate (VII) KMnO4 under acidic conditions. Potassium manganate can be replaced by other...

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Controlling Position of Equilibrium

Already know le Chatelier’s principle…  Concentration: If concentration increase, position of equilibrium shifts in direction that reduces concentration right/ left, so towards product/ reactants.  Pressure: If pressure increased, position of equilibrium shifts...

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Iodine/ Thiosulfate Redox Titrations

Iodine/ Thiosulfate Titrations: Oxidising agent must first oxidise I- ions to I2. Then thiosulfate ions S2O3 2- are oxidised and iodine reduced. Amount of iodine can be determined. As well iodine, other oxidising agents can be determined such as chlorate ions ClO- in...

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Bronsted- Lowry Acids and Bases

Acid: An acid dissociates and releases H+ ions in aqueous solution. A Bronsted- Lowry acid is a proton donor.  A strong acid completely dissociates AND a weak acid partially dissociates.  Can measure current through an acid to determine if strong and weak acid....

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Electrode Potentials

Voltaic Cell: A voltaic cell is a type of electrochemical cell, which converts chemical energy to electrical energy. Chemical energy from movement of electrons, so use redox reactions as they transfer electrons.  Half Cell: A half-cell contains species present in...

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pH Scale and Strong Acids

pH Scale: Uses negative logarithm of powers of 10. More manageable scale.  H Ion Concentration: Low value of [H+ (aq)] = high value of pH. A change in one pH number is 10x the [H+ (aq)].  Measuring pH: The electrode in pH meter measures electrical potential of H+...

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Predictions from Electrode Potentials

Predicting Feasibility: Can predict feasibility of reaction from standard electrode potentials. A reaction takes place when the one being reduced (and on left) has a more positive E o value than one being oxidised (and on right).  This works as higher E o value means...

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Acid Dissociation Constant Ka

Acid Dissociation Constant Ka: Tells us extent of dissociation. No Ka value for strong acid as completely dissociate. Units are moldm-3. Ka = [ H +(aq)][ A−(aq)] [ HA(aq)] Use this one if Q asks for Ka expression.  Equilibrium Constant: Ka changes with temperature so...

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Storage and Fuel Cells

Modern Cells and Batteries: Modern cells and batteries based on two electrodes with different electrode potentials. Three main times of cells- primary, secondary and fuel cells.  Primary Cells: Primary cells are non- rechargeable. Electricity is produced by oxidation...

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Orders, Rate Equations and Rate Constants

Rate = change in concentration/ change in time. [A] is shorthand for ‘concentration of A’.  Rate of Reaction: The change in concentration of a reactant or product per unit time.  Units: Usually it is mol dm-3 s-1. -1 in superscript means ‘per’ or ‘divide’.  Orders...

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Concentration- Time Graphs

Colorimeter: Monitoring colour change/ concentration. Amount of light absorbed by solution.  Experiment Method: Prepare standard solutions of known concentrations of solution. Choose filter with complementary colour to coloured chemical. Zero colorimeter with water....

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Rate- Concentration Graphs

Rate- Concentration Graphs:  Zero Order: Straight horizontal line with zero gradient. Rate = k[A]0 so rate = k = Y intercept. Reaction rate does not change with concentration. Can confirm first order of reaction of graph by calculating two half-lives and constant....

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Rate- Determining Step

Reaction Mechanism: Reactions take place in series of steps called reaction mechanism. - Collision unlikely between more than 2 species in one step. - Also stoichiometry in rate equation may not match overall equation.  Rate- Determining Step: The steps in reactions...

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Rate Constants and Temperature

Temperature Increase: As temperature increases, rate increases and the value of rate constant k increases. This is due to two factors…  Kinetic Energy: As temperature increases, particles move faster and collide more frequently.  Activation Energy: Increasing...

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