Notes

20.6 – Stereoisomerism

20.6 - Stereoisomerism 20.6.1 - Describe stereoisomers as compounds with the same structural formula but with different arrangements of atoms in space Stereoisomers have the same molecular and structural formula, but have different arrangements of atoms in space....

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20.5 – Reaction Pathways

20.5 - Reaction Pathways 20.5.1 - Deduce reaction pathways given the starting materials and the product Halogenoalkane to Amine Step 1 - 1-bromopropane reacts with KCN to form propanenitrile, using nucleophilic substitution Step 2 - Propanenitrile reacts with hydrogen...

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20.4 – Condensation Reactions

20.4 - Condensation Reactions 20.4.1 - Describe, using equations, the reactions of alcohols with carboxylic acids to form esters, and state the uses of esters Esters are formed in the reaction of carboxylic acids and alcohols, producing a small water molecule as a...

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20.3 – Elimination Reactions

20.3 - Elimination Reactions 20.3.1 - Describe, using equations, the elimination of HBr from bromoalkanes Halogenoalkanes can undergo both substitution and elimination reactions. The conditions determine the outcome of the reaction. When bromoethane is reacted in hot...

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20.2 – Nucleophilic Substitution Reactions

20.2 - Nucleophilic Substitution Reactions 20.2.1 - Explain why the hydroxide ion is a better nucleophile than water A nucleophile has a lone pair of electrons and is attracted to a positive nucleus. OH- is a stronger nucleophile than H2O because it has a negative...

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20.1 – Introduction

20.1 - Introduction 20.1.1 - Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: amine, amide, ester and nitrile   Amine This is the -NH2 functional group when present on the end of a carbon...

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19.2 – Electrolysis

19.2 – Electrolysis 19.2.1 - Predict and explain the products of electrolysis of aqueous solutions Electrolysis takes place in electrolytic cells, which means that the redox reaction takes place in reverse. Electricity is supplied to the cell to overcome the potential...

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19.1 – Standard Electrode Potentials

19.1 – Standard Electrode Potentials     19.1.1 - Describe the standard hydrogen electrode The standard hydrogen electrode is made up of an acidic solution, containing H+ ions in a concentration of 1.00 mol dm-3. There is also a platinum electrode sitting...

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18.5 – Indicators

18.5 – Indicators 18.5.1 - Describe qualitatively the action of an acid-base indicator Indicators change their colour depending on the pH of the solution. This is because they change forms depending on the H+ concentration, according to Le Chatelier’s principle. To...

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18.4 – Acid-Base Titrations

18.4 – Acid-Base Titrations 18.4.1 - Sketch the general shapes of graphs of pH against volume for titrations involving strong and weak acids and bases, and explain their important features When we perform a titration, we can sketch a titration curve to show how the pH...

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18.3 – Salt Hydrolysis

18.3 – Salt Hydrolysis 18.3.1 - Deduce whether salts form acidic, alkaline or neutral aqueous solution   Strong Acid and Strong Base The salt that is formed from a strong acid and a strong base will be neutral in solution. The Na+ and Cl- ions do not act as acids...

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18.2 – Buffer Solutions

18.2 – Buffer Solutions 18.2.1 - Describe the composition of a buffer solution and explain its action Buffer solutions maintain the pH of solutions by resisting changes caused by the addition of an acid or base.   Acidic Buffer Solution This is formed from a weak...

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18.1 – Calculations Involving Acids and Bases

18.1 – Calculations Involving Acids and Bases 18.1.1 - State the expression for the ionic product constant of water The ionisation of water happens according to the equation: Using this, we can find the expression of the equilibrium constant:   However, the...

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The Equilibrium Law

Solve homogeneous equilibrium problems using the expression for Kc A homogenous equilibrium system is when all the substances involved in the reaction are in the same state. For the reaction: The equilibrium constant expression is: This is valid, provided the...

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Liquid-Vapour Equilibrium 

Liquid-Vapour Equilibrium  Describe the equilibrium established between a liquid and its own vapour and how it is affected by temperature changes Vapour – A gas that is below its critical temperature. Critical Temperature – The highest temperature at which a gas can...

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Activation Energy

Describe qualitatively the relationship between the rate constant (k) and temperature (T) The relationship between reaction rate and temperature is that a 10oC rise in temperature will almost double the reaction rate. As the temperature rises, more of the molecules...

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Reaction Mechanism

Explain that reactions can occur by more than one step and that the slowest step determines the rate of reaction (the rate-determining step)  Reaction will take place in a series of steps, forming intermediate products in the process. This is because most reactions...

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Rate Expression

Rate Expression Distinguish between the terms rate constant, overall order of reaction and order of reaction with respect to a particular reactant  Rate is proportional to the concentration of reactants present. Using this relationship, the following equation was...

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Spontaneity

Predict whether a reaction or process will be spontaneous by using the sign of ΔGӨ The entropy and enthalpy both affect whether a reaction is spontaneous. The balance between these factors is found using Gibbs free energy, symbol G. This indicates whether a reaction...

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Entropy

State and explain the factors that increase the entropy in a system Entropy (symbol is S) is a measure of the randomness or disorder in a system. This tends to increase over time in a closed system. Gases mixing together increase the entropy. The disorder of a system...

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Born-Haber Cycles

Born-Haber Cycles Define and apply the terms lattice enthalpy and electron affinity  Lattice Enthalpy – The energy required to completely separate one mole of a solid ionic compound into its gaseous ions. Electron Affinity – The energy change that occurs when mole of...

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Standard Enthalpy Changes of Reaction

Define and apply the terms standard state, standard enthalpy change of formation, and standard enthalpy change of combustion Standard State The state that the substance is in at 298K [25°C] and 1atm [1.01 x 102kPa]. For elements, this is solid, liquid or gas. For...

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Delocalisation of Electrons

Delocalisation of Electrons  Describe the delocalisation of π electrons and explain how this can account for the structures of some species Not all molecules can be accurately represented by a single Lewis structure diagram. Some compounds are resonance structures,...

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Hybridisation

Hybridisation   Describe σ and π bonds   According to Lewis theory, covalent bonds consist of shared pairs of electrons, creating an area of electron density between the atoms. Also, atomic orbital theory states that electrons exist in atomic orbitals that are regions...

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Shapes of Molecules and Ions

Shapes of Molecules and Ions   Predict the shape and bond angles for species with five and six negative charge centres using the VSEPR theory Although most atoms will aim to form an octet of electrons, this rule can be broken in some cases, such as period 3 elements...

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13.2 – First-Row d-Block Elements

13.2.1 - List the characteristic properties of transition elements A variable oxidation number Higher melting points, harder and denser than group 1 and 2 metals Form complex ions Majority of their compounds are coloured Can act as catalysts No significant change in...

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Trends Across Period 3

Explain the physical states (under standards conditions) and electrical conductivity (in the molten state) of the chlorides and oxides of the elements in period 3 in terms of their bonding and structure Summary of Chlorides Summary of Oxides 13.1.2 - Describe the...

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12.1- Electron Configuration

Electron Configuration Explain how evidence form first ionisation energies across periods accounts for the existence of main energy levels and sub-levels in atoms First Ionisation Energy - The amount of energy required to remove one mole of electrons from one mole of...

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