HSC Chemistry Complete Course Definitive Study Guide

Module 5: Equilibrium and Acid Reactions

Static and Dynamic Equilibrium

• Reversible and Irreversible Reactions

  • Irreversible Reactions: Represented by a single left-to-right arrow ($\rightarrow$). Occur when reactants combine to form products, and the products are unable to convert back into reactants.

  • Reversible Reactions: Represented by a double equilibrium arrow ($\rightleftharpoons$). Occur when reactants combine to form products, and products can simultaneously convert back into reactants. Changing reaction conditions alters the proportion of reactants to products.

  • Practical Investigations of Reversibility:

    • Cobalt(II) Chloride Hydration/Dehydration:

      • Chemical Equation: $CoCl_2(aq) + 6H_2O(l) \rightleftharpoons CoCl_2 \times 6H_2O(l)$

      • Anhydrous form ($CoCl_2$): Sky blue colour. Contains no water molecules.

      • Hexahydrate form ($CoCl_2 \times 6H_2O$): Purple colour. Hydrated by six water molecules.

      • Observation: Adding water turns sky blue anhydrous cobalt(II) chloride purple. Heating/drying removes water and shifts the system back to sky blue, physically demonstrating reversibility.

      • Application: Used as a test for the presence of water.

    • Iron(III) Nitrate and Potassium Thiocyanate:

      • Ionic Equation: $Fe^{3+}(aq) + SCN^-(aq) \rightleftharpoons [FeSCN]^{2+}(aq)$

      • Observation: $Fe^{3+}$ ions are yellow in solution; potassium thiocyanate ($KSCN$) is clear. Reaction produces blood-red iron(III) thiocyanate ($[FeSCN]^{2+}$).

    • Burning Magnesium:

      • Chemical Equation: $2Mg(s) + O_2(g) \rightarrow 2MgO(s) + \text{energy}$

      • Classification: Irreversible reaction ($\rightarrow$).

      • Mechanism: Exothermic process releasing large amounts of heat and light energy. Reversing the reaction requires putting more energy back into the system than was released, making re-combination practically impossible.

    • Burning Steel Wool:

      • Chemical Equation: $4Fe(s) + 3O_2(g) \rightarrow 2Fe_2O_3(s)$

      • Classification: Irreversible reaction ($\rightarrow$).

      • Mechanism: Steel wool is primarily iron ($Fe$). Combustion releases significant energy, preventing reverse re-combination under standard conditions.

• Types of Equilibrium and System Types

  • Equilibrium State: A state reached over time by reversible reactions where the concentration of products and the concentration of reactants remain constant.

  • Dynamic Equilibrium:

    • Definition: Reached when the rate of the forward reaction equals the rate of the reverse reaction ($\text{rate}_{\text{forward}} = \text{rate}_{\text{reverse}} \neq 0$).

    • Particle Behavior: Macroscopic concentrations stay constant, but individual reactant and product particles continuously shift back and forth at equal rates.

  • Static Equilibrium:

    • Definition: Reached when all particles are at rest and the rates of both forward and reverse reactions are zero ($\text{rate}_{\text{forward}} = \text{rate}_{\text{reverse}} = 0$).

    • Mechanism: Common in irreversible reactions ($\rightarrow$) that go to completion, consuming all limiting reactants.

  • Open and Closed Systems:

    • Open Systems: Systems capable of exchanging both energy and matter with their surroundings. Equilibrium depends on external environmental parameters (temperature, pressure, gas composition).

    • Closed Systems: Systems isolated from exchanging matter with their surroundings (though energy exchange may occur). Reaches equilibrium based strictly on the internal reactants and products contained within the boundary.

    • Example (Water Thermal Equilibrium): Hot and cold water mixed inside an insulating box (closed system) reach a stable warm temperature independent of ambient conditions. If the lid is opened (open system), thermal energy interacts with the environment until room temperature is reached.

• Non-Equilibrium Systems

  • Irreversibility Factors: Reactions become irreversible in open systems when products escape to the surroundings (e.g., thermal energy, light, or gaseous products lost to the atmosphere).

  • Entropy ($S$) and Enthalpy ($H$):

    • Combustion reactions are strongly exothermic ($\times H < 0$) and increase entropy ($\times S > 0$). Reversing the reaction requires providing more energy than was lost and creating a greater increase in entropy elsewhere in the universe.

  • Photosynthesis:

    • Chemical Equation: $6CO_2(g) + 6H_2O(l) \rightarrow C_6H_{12}O_6(s) + 6O_2(g)$

    • Mechanism: Non-equilibrium process storing chemical potential energy in the chemical bonds of glucose. Work must be performed via a separate metabolic reaction pathway to break these bonds and release stored energy.

• Collision Theory and Reaction Rate

  • Collision Theory Model: Models gas particles as hard spheres moving in straight lines and colliding with container walls and each other.

  • Requirements for Reaction:

    1. Sufficient Energy: Colliding particles must possess kinetic energy equal to or greater than the activation energy ($E_a$) to break existing chemical bonds.

    2. Collision Event: Particles must physically collide. Reaction rate increases with collision frequency.

    3. Molecular Orientation: Particles must collide in the precise geometric orientation required to break and form specific molecular bonds.

  • Factors Increasing Reactions:

    • Concentration: Higher reactant concentration places more particles in a unit volume, increasing collision frequency.

    • Temperature: Increasing temperature increases the average kinetic energy and velocity of particles, increasing both collision frequency and the proportion of collisions exceeding $E_a$.

Factors that Affect Equilibrium

• Le Chatelier's Principle

  • Definition: "A system at equilibrium, when introduced to a change, will shift in equilibrium to minimise that change."

  • Thermal Definitions:

    • Endothermic: Absorbs thermal energy ($\times H^\text{o} > 0$).

    • Exothermic: Releases thermal energy ($\times H^\text{o} < 0$).

  • Molar Volume of Gases: At $25\text{ }^\text{o}\text{C}$, $1\text{ mol}$ of any ideal gas occupies approximately $24.79\text{ L}$.

  • Equilibrium Response Rules:

    • Concentration:

      • Increasing reactant concentration $\rightarrow$ Shifts right (towards products).

      • Increasing product concentration $\rightarrow$ Shifts left (towards reactants).

    • Pressure (Gaseous Systems):

      • Increasing total pressure $\rightarrow$ Shifts to the side with fewer total moles of gas.

      • Decreasing total pressure $\rightarrow$ Shifts to the side with more total moles of gas.

    • Temperature:

      • Increasing temperature $\rightarrow$ Shifts in the endothermic direction to absorb added heat.

      • Decreasing temperature $\rightarrow$ Shifts in the exothermic direction to release heat.

• Experimental Applications of Le Chatelier's Principle

  • Cobalt(II) Chloride Hydrate System:

    • Equation: $CoCl_2(aq) + 6H_2O(l) \rightleftharpoons CoCl_2 \times 6H_2O(l)$

    • Thermochemistry: The hydration reaction is exothermic ($\times H^\text{o} < 0$).

    • Effect of Heating: Increasing temperature shifts equilibrium to the left (endothermic dehydration step), turning the purple solution sky blue.

  • Nitrogen Dioxide and Dinitrogen Tetroxide System:

    • Chemical Equation: $2NO_2(g) \rightleftharpoons N_2O_4(g)$

    • Enthalpy: $\times H^\text{o} = -57.20\text{ kJ }mol^{-1}$ (Exothermic forward reaction).

    • Concentration Change: Adding $NO_2(g)$ shifts equilibrium right to form $N_2O_4(g)$.

    • Pressure Change: Increasing container pressure shifts equilibrium right (2 moles of gas $\rightarrow$ 1 mole of gas).

    • Temperature Change: Increasing temperature shifts equilibrium left (endothermic direction), increasing $NO_2(g)$ yield.

    • Maximising Yield Strategy: Continuous addition of $NO_2$, continuous removal of $N_2O_4$, maximum feasible pressure, and lowest economically viable temperature.

    • Industrial Constraint: High pressures increase plant operational costs and equipment failure hazards.

  • Iron(III) Thiocyanate System:

    • Chemical Equation: $Fe^{3+}(aq) + SCN^-(aq) \rightleftharpoons [FeSCN]^{2+}(aq)$

    • Colour Profiles: $Fe^{3+}$ (yellow), $SCN^-$ (colourless), $[FeSCN]^{2+}$ (blood red).

    • Observation: Adding $Fe^{3+}$ or $SCN^-$ deepens red intensity (shift right). Adding species that complex with $Fe^{3+}$ lightens colour to yellow (shift left).

• Equilibrium and Collision Theory

  • Concentration: Higher concentration increases particle number density, increasing successful collisions per second for that reaction direction.

  • Pressure: Higher gas pressure increases particle density, increasing collision rate disproportionately on the side with more gaseous molecules.

  • Temperature: Higher temperature increases particle speed and kinetic energy distribution, increasing the fraction of collisions with $E \rightleftharpoons E_a$ for endothermic pathways relative to exothermic pathways.

Calculating the Equilibrium Constant Keq

• The Equilibrium Expression

  • Homogeneous Reaction: A reaction where all reactants and products exist in a single phase (e.g., all aqueous or all gaseous).

  • Heterogeneous Reaction: A reaction where reactants and products exist in multiple physical phases (e.g., solid and gas).

  • General Expression: For the general homogenous equation $aA + bB \rightleftharpoons cC + dD$         $K_{eq} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$

    • Upper-case letters ($A, B, C, D$) denote chemical species concentrations at equilibrium in $mol\text{ }L^{-1}$.

    • Lower-case letters ($a, b, c, d$) represent stoichiometric coefficients.

• Quantitative Applications of Keq

  • Interpretation of Values:

    • $K_{eq} < 1$: Equilibrium mixture contains predominantly reactants.

    • $K_{eq} > 1$: Equilibrium mixture contains predominantly products.

  • ICE Table Method (Initial, Change, Equilibrium):

    1. Write balanced chemical equation.

    2. Construct table with columns for each chemical species and rows for Initial Moles/Concentration, Change, and Equilibrium/Final Concentration.

    3. Express changes using stoichiometric ratios $x$.

    4. Convert all quantities to concentration ($c = \frac{n}{V}$) before calculating $K_{eq}$.

• Sample Calculations

  • Ammonia Synthesis:

    • Equation: $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$

    • Data at Equilibrium: $[NH_3] = 2 \times 10^{-2}\text{ mol }L^{-1}$, $[N_2] = 3.1 \times 10^{-3}\text{ mol }L^{-1}$, $[H_2] = 1.2 \times 10^{-2}\text{ mol }L^{-1}$

    • Calculation:             $K_{eq} = \frac{[NH_3]^2}{[N_2][H_2]^3} = \frac{(2 \times 10^{-2})^2}{(3.1 \times 10^{-3})(1.2 \times 10^{-2})^3} = 7.5 \times 10^4$

  • Nitrosyl Chloride Formation:

    • Equation: $ClNO_2(g) + NO(g) \rightleftharpoons NO_2(g) + ClNO(g)$

    • System: $1.0\text{ L}$ container filled with $0.1\text{ mol}$ $ClNO_2$. At equilibrium, $0.03\text{ mol}$ $ClNO_2$ and $0.01\text{ mol}$ $NO$ remain.

    • ICE Analysis:

      • $\times[ClNO_2] = 0.1 - 0.03 = -0.07\text{ mol }L^{-1}$

      • $[NO]_{\text{initial}} = 0.01 - (-0.07) = 0.08\text{ mol }L^{-1}$

      • $[NO_2]_{\text{final}} = [ClNO]_{\text{final}} = +0.07\text{ mol }L^{-1}$

    • Calculation:             $K_{eq} = \frac{(0.07)(0.07)}{(0.03)(0.01)} = 16.3$

  • Hydrogen Iodide Decomposition:

    • Equation: $2HI(g) \rightleftharpoons H_2(g) + I_2(g)$

    • System: $5.0\text{ L}$ container filled with $1.8\text{ mol}$ $HI$. Equilibrium $n(I_2) = 0.55\text{ mol}$.

    • Concentrations at Equilibrium:

      • $[I_2] = \frac{0.55}{5.0} = 0.11\text{ mol }L^{-1}$

      • $[H_2] = 0.11\text{ mol }L^{-1}$

      • $[HI] = \frac{1.8 - (2 \times 0.55)}{5.0} = \frac{0.70}{5.0} = 0.14\text{ mol }L^{-1}$

    • Calculation:             $K_{eq} = \frac{(0.11)(0.11)}{(0.14)^2} = 0.62$

  • Reaction Quotient Evaluation:

    • System: $0.75\text{ L}$ vessel containing $2.00\text{ mol}$ $CH_4$, $0.75\text{ mol}$ $H_2O$, $1.25\text{ mol}$ $CO$, $0.75\text{ mol}$ $H_2$.

    • Equation: $CH_4(g) + H_2O(g) \rightleftharpoons CO(g) + 3H_2(g)$, with $K_{eq} = 0.55$

    • Concentrations: $[CH_4] = 2.67\text{ mol }L^{-1}$, $[H_2O] = 1.00\text{ mol }L^{-1}$, $[CO] = 1.67\text{ mol }L^{-1}$, $[H_2] = 1.00\text{ mol }L^{-1}$

    • Quotient ($Q$):             $Q = \frac{[H_2]^3[CO]}{[H_2O][CH_4]} = \frac{(1.00)^3(1.67)}{(1.00)(2.67)} = 0.625$

    • Conclusion: Since $Q (0.625) > K_{eq} (0.55)$, the system is not at equilibrium and will shift left towards reactants.

  • Hydrogen Gas Ionisation:

    • Equation: $H_2(g) \rightleftharpoons 2H^+(aq)$

    • System: $5.0\text{ L}$ vessel. $K_{eq} = 3.3 \times 10^{-4}$. Equilibrium $n(H^+) = 1 \times 10^{-2}\text{ mol}$.

    • Calculation:

      • $[H^+] = \frac{1 \times 10^{-2}}{5.0} = 2 \times 10^{-3}\text{ mol }L^{-1}$

      • $[H_2]_{\text{final}} = \frac{[H^+]^2}{K_{eq}} = \frac{(2 \times 10^{-3})^2}{3.3 \times 10^{-4}} = 0.01212\text{ mol }L^{-1}$

      • $n(H_2)_{\text{final}} = 0.01212 \times 5.0 = 0.0606\text{ mol}$

      • $\times n(H_2) = \frac{1}{2} \times (1 \times 10^{-2}) = 0.005\text{ mol}$

      • $n(H_2)_{\text{initial}} = 0.0606 + 0.005 = 0.0656\text{ mol} \rightleftharpoons 0.071\text{ mol}$

  • Quadratic Solution Method for Unknown Equilibrium Moles:

    • Equation: $2NO_2(g) \rightleftharpoons N_2O_4(g)$, $K_{eq} = 1.044$, $V = 2.0\text{ L}$.

    • Initial Moles: $n(NO_2) = 4.5\text{ mol}$, $n(N_2O_4) = 2.25\text{ mol}$.

    • Algebraic ICE Table:

      • $[NO_2]_{\text{final}} = \frac{4.5 - 2x}{2}$

      • $[N_2O_4]_{\text{final}} = \frac{2.25 + x}{2}$

      • $K_{eq} = \frac{\frac{2.25 + x}{2}}{\frac{(4.5 - 2x)^2}{4}} = \frac{2(2.25 + x)}{(4.5 - 2x)^2} = 1.044$

      • Expanding to quadratic form $ax^2 + bx + c = 0$:                 $2.088x^2 - 10.396x + 8.3205 = 0$

      • Applying quadratic formula $x = \frac{-b \times \times\text{b}^2 - 4ac}{2a}$ yields $x = 3.98$ or $x = 1.00$.

      • Selection: $x = 3.98$ yields a negative molar quantity for $NO_2$ ($4.5 - 2(3.98) = -3.46\text{ mol}$), which is physically impossible. Therefore, $x = 1.00\text{ mol}$.

      • Final Moles: $A = n(NO_2) = 2.5\text{ mol}$, $B = n(N_2O_4) = 3.25\text{ mol}$.

• Temperature Effects on Keq

  • Rule: Temperature is the only variable that alters the value of $K_{eq}$.

  • Exothermic Reactions: Increasing temperature decreases $K_{eq}$.

  • Endothermic Reactions: Increasing temperature increases $K_{eq}$.

• Equilibrium Constants for Dissociation

  • Ionic Solutions:

    • $NaCl(s) \rightleftharpoons Na^+(aq) + Cl^-(aq)$

    • $K_{eq} = \frac{[Na^+][Cl^-]}{[NaCl]}$

  • Acid Dissociation ($K_a$):

    • General Equation: $HA(aq) + H_2O(l) \rightleftharpoons A^-(aq) + H_3O^+(aq)$

    • Acid Dissociation Constant ($K_a$):             $K_a = \frac{[A^-][H_3O^+]}{[HA]} \rightleftharpoons \frac{[A^-][H^+]}{[HA]}$

    • Note: Water concentration is omitted from the expression as its concentration remains essentially constant ($1$).

Solution Equilibria

• Polarity and Molecular Geometry

  • Polarity: Measure of electric charge distribution. Represented using partial charge notation ($\times^+$ and $\times^-$).

  • Boron Trichloride ($BCl_3$): Non-polar, trigonal planar geometry with $120^\text{o}$ bond angles due to symmetric electron repulsion.

  • Water ($H_2O$): Highly polar. Oxygen retains 2 non-bonding lone electron pairs, creating a bent molecular shape with permanent dipoles.

• Intermolecular Forces

  1. Dispersion Forces: Weakest intermolecular force. Temporary induced dipoles formed by unsymmetrical electron density distribution.

  2. Dipole-Dipole Forces: Intermediate strength. Electrostatic attraction between permanent partial positive and negative dipoles in polar molecules.

  3. Hydrogen Bonding: Strongest intermolecular force. Occurs between hydrogen bonded to highly electronegative atoms ($F$, $O$, $N$) and adjacent unbonded lone pairs.

  • Dissolution Mechanism: Positive cations attract partial negative oxygen atoms ($\times^-$) of water; negative anions attract partial positive hydrogen atoms ($\times^+$).

• Applications and Indigenous Knowledge

  • Cycad Fruit Detoxification by Aboriginal Peoples:

    • Context: Cycad fruit contains highly toxic, carcinogenic soluble compounds.

    • Method: Fruit was cut open and submerged in flowing streams/rivers.

    • Chemical Mechanism: Dissolution establishes equilibrium: $\text{Toxin}(s) \rightleftharpoons \text{Toxin}(aq)$.

    • Le Chatelier's Application: Flowing water continuously removes aqueous toxins, driving $[\text{Toxin}(aq)] \rightarrow 0$. By Le Chatelier's principle, the system shifts right continuously until all solid toxins leach out.

• Solubility Rules

  • NAGSAG (Always Soluble):

    • Nitrates ($NO_3^-$)

    • Acetates ($C_2H_3O_2^-$)

    • Group 1 Alkali Metals ($Li^+$, $Na^+$, $K^+$, etc.)

    • Sulphates ($SO_4^{2-}$)

    • Ammonium ($NH_4^+$)

    • Group 7 Halides ($Cl^-$, $Br^-$, $I^-$)

  • Exceptions:

    • PMS (Insoluble with Sulphates and Group 7): Pb$^{2+}$ (Lead), Mercury, Silver ($Ag^+$).

    • CASTROBeAR (Insoluble with Sulphates): Ca$^{2+}$ (Calcium), Sr$^{2+}$ (Strontium), Ba$^{2+}$ (Barium).

  • Standard Reduction Potentials and Metal Activity:

    • $K^+ + e^- \rightleftharpoons K(s)$ ($-2.94\text{ V}$)

    • $Ba^{2+} + 2e^- \rightleftharpoons Ba(s)$ ($-2.91\text{ V}$)

    • $Ca^{2+} + 2e^- \rightleftharpoons Ca(s)$ ($-2.87\text{ V}$)

    • $Na^+ + e^- \rightleftharpoons Na(s)$ ($-2.71\text{ V}$)

    • $Mg^{2+} + 2e^- \rightleftharpoons Mg(s)$ ($-2.36\text{ V}$)

    • $Al^{3+} + 3e^- \rightleftharpoons Al(s)$ ($-1.68\text{ V}$)

    • $Mn^{2+} + 2e^- \rightleftharpoons Mn(s)$ ($-1.18\text{ V}$)

    • $H_2O + e^- \rightleftharpoons \frac{1}{2}H_2(g) + OH^-$ ($-0.83\text{ V}$)

    • $Zn^{2+} + 2e^- \rightleftharpoons Zn(s)$ ($-0.76\text{ V}$)

    • Rule: A more active metal (higher on standard potentials list) displaces a less active metal ion from solution.

• Solubility Product ($K_{sp}$)

  • Definition: For dissolution $AB(s) \rightleftharpoons A^+(aq) + B^-(aq)$, $K_{sp} = [A^+][B^-]$.

  • Example ($AgCl$ Dissolution):

    • $AgCl(s) \rightleftharpoons Ag^+(aq) + Cl^-(aq)$, $K_{sp} = 2 \times 10^{-10}$ at $25\text{ }^\text{o}\text{C}$.

    • Molar Concentration: $[Ag^+] = [Cl^-] = \times 2 \times 10^{-10} = 1.41 \times 10^{-5}\text{ mol }L^{-1}$

    • Mass Dissolved per Litre: $m = n \times MM = (1.41 \times 10^{-5}) \times 143.32 = 0.002\text{ g}$

    • Solubility: $0.002\text{ g }L^{-1}$.

• Precipitate Calculations

  • System: $1.3\text{ g}$ $KI(s)$ added to $100\text{ mL}$ of $0.11\text{ mol }L^{-1}$ $Pb(NO_3)_2(aq)$. $K_{sp}(PbI_2) = 4.4 \times 10^{-9}$.

  • Reaction: $2KI(s) + Pb(NO_3)_2(aq) \rightleftharpoons PbI_2(s) + 2KNO_3(aq)$

  • Initial Moles:

    • $n(KI) = \frac{1.3}{166.0028} = 0.0078\text{ mol}$

    • $n(Pb(NO_3)_2) = 0.11 \times 0.1 = 0.011\text{ mol}$

  • Limiting Reagent Analysis: $0.0078\text{ mol}$ $KI$ reacts completely with $0.0039\text{ mol}$ $Pb(NO_3)_2$, producing $0.0039\text{ mol}$ $PbI_2(s)$.

  • Dissolution Equilibrium ($PbI_2(s) \rightleftharpoons Pb^{2+} + 2I^-$):

    • $K_{sp} = [Pb^{2+}][I^-]^2 = [Pb^{2+}](2[Pb^{2+}])^2 = 4[Pb^{2+}]^3 = 4.4 \times 10^{-9}$

    • $[Pb^{2+}] = \times{\frac{4.4 \times 10^{-9}}{4}} = 0.001032\text{ mol }L^{-1}$

    • Moles Dissolved in $0.1\text{ L}$: $n = 0.001032 \times 0.1 = 0.000103\text{ mol}$

  • Precipitate Remaining:         $n(\text{precipitate}) = 0.0039 - 0.000103 = 0.003797\text{ mol}$

Module 6: Acid/Base Reactions

Properties of Acids and Bases

• IUPAC Nomenclature and Chemical Formulas

  • Hydrofluoric acid: $HF$

  • Hydrochloric acid: $HCl$

  • Nitrous acid: $HNO_2$

  • Nitric acid: $HNO_3$

  • Sulphurous acid: $H_2SO_3$

  • Sulphuric acid: $H_2SO_4$

  • Phosphoric acid: $H_3PO_4$

  • Carbonic acid: $H_2CO_3$

  • Acetic acid (Ethanoic acid): $CH_3COOH$

  • Citric acid: $C_6H_8O_7$

  • Sodium hydroxide: $NaOH$

  • Barium hydroxide: $Ba(OH)_2$

  • Ammonia: $NH_3$

• Modern Definitions

  • Acid: Proton ($H^+$) donor.

  • Base: Proton ($H^+$) acceptor.

• Predicting Products of Acid Reactions

  • Acids and Bases (Neutralisation):

    • $\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}$

    • Example 1: $NaOH(aq) + HCl(aq) \rightarrow NaCl(aq) + H_2O(l)$

    • Example 2: $2HCl(aq) + Ba(OH)_2(aq) \rightarrow BaCl_2(aq) + 2H_2O(l)$

  • Acids and Carbonates:

    • $\text{Acid} + \text{Carbonate} \rightarrow \text{Salt} + \text{Water} + \text{Carbon Dioxide}$

    • Example 1: $2HCl(aq) + Na_2CO_3(aq) \rightarrow 2NaCl(aq) + H_2O(l) + CO_2(g)$

    • Example 2: $H_2SO_4(aq) + CuCO_3(s) \rightarrow CuSO_4(aq) + H_2O(l) + CO_2(g)$

  • Acids and Metals:

    • $\text{Acid} + \text{Metal} \rightarrow \text{Salt} + \text{Hydrogen Gas}$

    • Example: $H_2SO_4(aq) + Mg(s) \rightarrow MgSO_4(aq) + H_2(g)$

• Applications and Enthalpy of Neutralisation

  • Everyday & Industrial Applications: Neutralisation of industrial wastewater, pH balancing of swimming pools, municipal drinking water purification, and stomach acid ($HCl$) neutralisation by pancreatic secretions in the duodenum.

  • Net Ionic Neutralisation Equation:         $H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$

  • Enthalpy Change: All neutralisation reactions are exothermic, with a standard enthalpy change of $\times H = -57.30\text{ kJ }mol^{-1}$.

• Historical Development of Acid-Base Models

  • Antoine Lavoisier (1776):

    • Theory: Proposed that acids were binary compounds containing oxygen atoms.

    • Limitation: Many strong acids (e.g., Hydrochloric acid $HCl$) contain no oxygen.

  • Humphry Davy (1810):

    • Theory: Proposed that acids contained replaceable hydrogen atoms that could be displaced by metals.

    • Limitation: Lacked a molecular mechanism explaining how or why acids interact in solution.

  • Svante Arrhenius (1884):

    • Theory: Defined acids as substances that ionise in aqueous solution to yield hydrogen ions ($H^+$), and bases as substances that ionise to yield hydroxide ions ($OH^-$).

    • Limitation: Restricted strictly to aqueous solutions; cannot explain non-aqueous acid-base interactions or basicity of species lacking hydroxide ions (e.g., $NH_3$ gas).

  • Johannes Brønsted & Thomas Lowry (1923):

    • Theory: Defined acids as proton donors and bases as proton acceptors. Operates independently of solvent.

    • Limitation: Requires presence of hydrogen/protons; cannot explain acidic behaviour of electron-deficient species lacking hydrogen (e.g., $BF_3$ or $AlCl_3$).

Using Brønsted-Lowry Theory

• Quantitative Acid-Base Relationships

  • Core Mathematical Equations:

    • $c = \frac{n}{V}$

    • $n = \frac{m}{MM}$

    • $pH = -\text{log}_{10}[H^+]$

    • $pOH = -\text{log}_{10}[OH^-]$

    • $pH + pOH = 14$

    • $[H^+] = 10^{-pH}$

    • $[OH^-] = 10^{-pOH}$

  • Ionisation Differences:

    • Strong Acids/Bases: Ionise completely in solution ($\rightarrow$).

    • Weak Acids/Bases: Ionise partially in solution, establishing dynamic equilibrium ($\rightleftharpoons$).

• Sample Quantitative Calculations

  • Calculations from Hydrogen Ion Concentration:

    • Given: $[H^+] = 0.02\text{ mol }L^{-1}$

    • $pH = -\text{log}_{10}(0.02) = 1.7$

    • $pOH = 14 - 1.7 = 12.3$

  • Concentration from pOH:

    • Given: $pOH = 13.3$

    • $14 + \text{log}_{10}[H^+] = 13.3 \rightarrow \text{log}_{10}[H^+] = -0.7$

    • $[H^+] = 10^{-0.7} = 0.20\text{ mol }L^{-1}$

  • pH of Solid Dissolved Strong Base:

    • Given: $2.30\text{ g}$ $NaOH$ in $250\text{ mL}$ solution.

    • $n(NaOH) = \frac{2.30}{39.998} = 0.0575\text{ mol}$

    • $[OH^-] = \frac{0.0575}{0.250} = 0.230\text{ mol }L^{-1}$

    • $pOH = -\text{log}_{10}(0.230) = 0.639$

    • $pH = 14 - 0.639 = 13.36$

  • pH of Mixed Strong Acid and Strong Base Solution:

    • Given: $125\text{ mL}$ of $0.30\text{ mol }L^{-1}$ $HCl$ mixed with $25\text{ mL}$ of $1.3\text{ mol }L^{-1}$ $NaOH$

    • $n(H^+) = 0.30 \times 0.125 = 0.0375\text{ mol}$

    • $n(OH^-) = 1.3 \times 0.025 = 0.0325\text{ mol}$

    • Excess $n(H^+) = 0.0375 - 0.0325 = 0.0050\text{ mol}$

    • Total Volume $V = 0.125 + 0.025 = 0.150\text{ L}$

    • $[H^+] = \frac{0.0050}{0.150} = 0.0333\text{ mol }L^{-1}$

    • $pH = -\text{log}_{10}(0.0333) = 1.48$ (Note: using exact values yields $pH = 1.41$ for $[H^+] = 0.0392\text{ mol }L^{-1}$).

  • Dilution and Reaction Neutralisation Calculation:

    • Given: $250\text{ mL}$ of $0.33\text{ mol }L^{-1}$ $HNO_3$ added to $500\text{ mL}$ of $0.1\text{ mol }L^{-1}$ $KOH$

    • $n(HNO_3) = 0.25 \times 0.33 = 0.0825\text{ mol}$

    • $n(KOH) = 0.50 \times 0.10 = 0.0500\text{ mol}$

    • Excess $n(H^+) = 0.0825 - 0.0500 = 0.0325\text{ mol}$

    • Total Volume $V = 0.25 + 0.50 = 0.75\text{ L}$

    • $[H^+] = \frac{0.0325}{0.75} = 0.0433\text{ mol }L^{-1}$

    • $pH = -\text{log}_{10}(0.0433) = 1.36$

• Conjugate Pairs and Amphiprotic Species

  • Conjugate Pairs: Acid-base pairs differing by a single proton ($H^+$).

    • $\text{Acid} \rightleftharpoons \text{Proton} + \text{Conjugate Base}$

    • $\text{Base} + \text{Proton} \rightleftharpoons \text{Conjugate Acid}$

    • Examples: $NH_4^+$ (acid) / $NH_3$ (conjugate base); $HF$ (acid) / $F^-$ (conjugate base).

  • Amphiprotic Nature: Ability of a molecule/ion to either donate or accept protons depending on reaction conditions.

    • Water ($H_2O$):

      • As proton donor: $Cl^-(aq) + H_2O(l) \rightarrow HCl(aq) + OH^-(aq)$

      • As proton acceptor: $NH_4^+(aq) + H_2O(l) \rightarrow NH_3(aq) + H_3O^+(aq)$

    • Hydrogen Carbonate ($HCO_3^-$):

      • As proton donor: $HCO_3^-(aq) \rightleftharpoons CO_3^{2-}(aq) + H^+(aq)$

      • As proton acceptor: $HCO_3^-(aq) + H^+(aq) \rightleftharpoons H_2CO_3(aq)$

    • Dihydrogen Phosphate ($H_2PO_4^-$):

      • As proton donor: $H_2PO_4^-(aq) \rightleftharpoons HPO_4^{2-}(aq) + H^+(aq)$

      • As proton acceptor: $H_2PO_4^-(aq) + H^+(aq) \rightleftharpoons H_3PO_4(aq)$

Quantitative Analysis

• Titration and Volumetric Analysis

  • Standard Solution Preparation:

    • Primary Standard Criteria: High purity, known molecular formula, high molar mass, water-soluble, non-hygroscopic (does not absorb atmospheric water), and chemically stable in air.

    • Procedure:

      1. Mass accurately using electronic balance.

      2. Dissolve completely in distilled water inside a beaker.

      3. Quantitative transfer into volumetric flask with beaker and glass rod washings.

      4. Fill with distilled water until lower meniscus touches calibration line.

      5. Stopper and invert multiple times to ensure homogeneity.

  • Indicator Selection:

    • Strong Acid + Strong Base: Equivalence point $pH \rightleftharpoons 7.0$ (Indicator: Bromothymol Blue).

    • Strong Acid + Weak Base: Equivalence point $pH \rightleftharpoons 4.0 - 5.0$ (Indicator: Methyl Orange).

    • Weak Acid + Strong Base: Equivalence point $pH \rightleftharpoons 8.5 - 10.0$ (Indicator: Phenolphthalein).

  • Sample Titration Calculation:

    • Data: $25.0\text{ mL}$ of $1.1\text{ mol }L^{-1}$ $NaOH$ neutralises $27.8\text{ mL}$ $HCl$ titrant.

    • $n(NaOH) = 1.1 \times 0.0250 = 0.0275\text{ mol}$

    • $n(HCl) = 0.0275\text{ mol}$ (1:1 stoichiometry)

    • $[HCl] = \frac{0.0275}{0.0278} = 0.989\text{ mol }L^{-1} \rightleftharpoons 0.99\text{ mol }L^{-1}$

• Titration Curves and Conductivity Profiles

  • Titration Curves:

    • Plots $pH$ versus volume of added titrant.

    • Strong Acid/Strong Base: Symmetrical curve with steep inflection centred at pH = 7.0$.\n * *Strong Acid/Weak Base*: Inflection shifted to acidic region (pH = 3.0 - 5.0).\n * *Weak Acid/Strong Base*: Inflection shifted to basic region (pH = 8.5 - 11.0).\n * **Conductivity Curves**:\n * Conductivity depends on ion concentration and mobility (H^+$and$OH^- have highest conductivities).\n * *Strong Acid/Strong Base curve*: High initial conductivity drops linearly to a sharp minimum at equivalence point as H^+$reacts with$OH^-$to form non-conductive$H_2O$. Conductivity rises linearly past equivalence due to excess$OH^- titrant.\n\n* **Dissociation Constants (K_a$and$pK_a)**\n * ext{pK}a = - ext{log}{10}(K_a)\n * High K_a$/ Low$pK_a$$ ightarrow Strong Acid.\n * Low K_a$/ High$pK_a$$ ightarrow Weak Acid.\n * **Comparative Values**:\n * Sulphuric acid (H_2SO_4$):$K_a = 1.2 imes 10^{-2}$,$pK_a = 1.92\n * Nitrous acid (HNO_2$):$K_a = 4.0 imes 10^{-4}$,$pK_a = 3.40\n * Carbonic acid (H_2CO_3$):$K_a = 4.8 imes 10^{-11}$,$pK_a = 10.32\n\n* **Applications and Buffers**\n * **Applications**: Industrial wastewater neutralisation, municipal water supply treatment (alkalinity management for flocculation), food industry quality control (titrating acids/salts), and rain acidification monitoring.\n * **Buffer Solutions**:\n * *Definition*: Solutions containing a weak acid and its conjugate base (or weak base and conjugate acid) that resist changes in pH upon addition of small quantities of acid or base.\n * *Blood Buffer System*: Carbonic acid / Hydrogen carbonate buffer system:\n            H_2CO_3(aq) + H_2O(l) ightleftharpoons HCO_3^-(aq) + H_3O^+(aq)\n * *Mechanism*: Excess CO_2$(e.g., from exercise) increases$[H_2CO_3]$, shifting equilibrium right to minimise$pH$rise; excess base reacts with$H_3O^+, shifting equilibrium right to replenish protons.\n\n# Module 7: Organic Chemistry\n\n## Nomenclature of Organic Compounds\n\n* **IUPAC Naming Conventions (Up to C8)**\n * **Carbon Chain Prefixes**: 1: Meth-, 2: Eth-, 3: Prop-, 4: But-, 5: Pent-, 6: Hex-, 7: Hept-, 8: Oct-.\n * **Alkanes**: Saturated hydrocarbons containing single C-C$bonds only. General formula:$C_nH_{2n+2}. Suffix: *-ane*.\n * **Alkenes**: Unsaturated hydrocarbons with at least one C=C$double bond. General formula:$C_nH_{2n}. Suffix: *-ene*. Numbered from chain end giving lowest position integer to double bond.\n * **Alkynes**: Unsaturated hydrocarbons with at least one C ightleftharpoons C$triple bond. General formula:$C_nH_{2n-2}. Suffix: *-yne*.\n * **Alcohols**: Contain hydroxyl group (-OH). Suffix: *-ol*.\n * *Primary Alcohol*: Carbon carrying -OH attached to 1 alkyl group.\n * *Secondary Alcohol*: Carbon carrying -OH attached to 2 alkyl groups.\n * *Tertiary Alcohol*: Carbon carrying -OH attached to 3 alkyl groups (e.g., 2-methylpropan-2-ol or *tert*-butyl alcohol).\n * **Aldehydes and Ketones**:\n * *Aldehyde*: Carbonyl group (C=O) at chain termination bonded to hydrogen. Suffix: *-al* (e.g., Methanal, Ethanal).\n * *Ketone*: Carbonyl group (C=O) located internally between two alkyl groups. Suffix: *-one* (e.g., Propanone, 2-Pentanone).\n * **Carboxylic Acids**: Contain carboxyl group (-COOH). Suffix: *-oic acid*.\n * 1 Carbon: Methanoic acid (Formic acid, HCOOH)\n * 2 Carbons: Ethanoic acid (Acetic acid, CH_3COOH)\n * 3 Carbons: Propanoic acid (Propionic acid, C_2H_5COOH)\n * 4 Carbons: Butanoic acid (Butyric acid, C_3H_7COOH)\n * 5 Carbons: Pentanoic acid (Valeric acid, C_4H_9COOH)\n * 6 Carbons: Hexanoic acid (Caproic acid, C_5H_{11}COOH)\n * 7 Carbons: Heptanoic acid (Enanthic acid, C_6H_{13}COOH)\n * 8 Carbons: Octanoic acid (Caprylic acid, C_7H_{15}COOH)\n * **Amines**: Contain amino group (-CNH_2). Suffix: *-amine* (e.g., Methanamine, Ethanamine).\n * **Amides**: Contain amide group (-CONH_2). Suffix: *-amide* (e.g., Methanamide, Ethanamide).\n * **Halogenated Hydrocarbons**: Halogen substituents named as prefixes: Fluorine (*Fluoro-*), Chlorine (*Chloro-*), Bromine (*Bromo-*), Iodine (*Iodo-*). Uses structural locants (1-, 2-) and multiplicity prefixes (*di-*, *tri-*). Chain direction selected to give the lowest locant sum.\n\n* **Structural Isomerism**\n 1. **Chain Isomers**: Isomers with identical molecular formulas but differing carbon backbone arrangements (e.g., Pentane, Isopentane / 2-methylbutane, Neopentane / 2,2-dimethylpropane).\n 2. **Position Isomers**: Isomers with identical carbon backbones but differing positions of functional groups or double/triple bonds (e.g., Propan-1-ol vs Propan-2-ol).\n 3. **Functional Group Isomers**: Isomers with identical molecular formulas containing entirely different functional groups (e.g., Cyclohexane vs Hex-1-ene, both C_6H_{12}).\n\n## Hydrocarbons: Structure, Bonding, and Reactivity\n\n* **Physical Properties and Homologous Series**\n * **Homologous Series**: Family of organic compounds with same functional group, similar chemical properties, and successive members differing by a -CH_2- unit.\n * **Boiling Point Trends**: Boiling point increases with carbon chain length/molecular mass due to increasing strength of intermolecular dispersion forces.\n\n* **Molecular Geometry**\n * **3D Representation**: Wedged bonds denote bonds extending forward out of page; dotted bonds denote bonds extending backward into page.\n * **Single-bonded Carbon (sp^3$)**: Tetrahedral spatial arrangement with bond angles of$109.5^ ext{o}$(e.g., Methane$CH_4).\n * **Double-bonded Carbon (sp^2$)**: Trigonal planar spatial arrangement with bond angles of$120^ ext{o} (e.g., Methanal).\n * **Triple-bonded Carbon (sp$)**: Linear spatial arrangement with bond angles of$180^ ext{o} (e.g., Ethyne).\n\n* **Safety and Environmental Implications**\n * **Laboratory Safety**: Organic solvents are flammable and volatile. Avoid open flames (use hot plates), conduct handling in fume hoods, and maintain fire blankets/extinguishers.\n * **Disposal**: Waste organic liquids must be collected in dedicated chlorinated or non-chlorinated solvent waste containers; never poured down municipal sinks.\n * **Socioeconomic & Environmental Impact Analysis**:\n * *Environmental*: Open-cut extraction causes ecosystem destruction. Combustion releases greenhouse gases (CO_2$), particulate soot (respiratory illnesses),$CO$(toxic), and$SO_2 (acid rain). Non-biodegradable synthetic polymers accumulate in landfills.\n * *Economic*: Petrochemicals drive energy generation and resource economies (mining boom), but overreliance stifles investment in alternative renewable markets.\n * *Sociocultural*: Energy reliance leads to global geopolitical instability. Mining activities often extinguish Native Title rights for Indigenous communities.\n * *Biomass Alternatives*: Renewable materials (plant waste) recycle atmospheric CO_2. Limitations include land diversion from food crops, soil erosion, and higher production costs.\n\n## Products of Reactions Involving Hydrocarbons\n\n* **Addition Reactions of Unsaturated Hydrocarbons**\n * **Hydrogenation**: Reaction with H_2(g)\n         ext{Ethene} + H_2 ightarrow ext{Ethane}\n        C_2H_4(g) + H_2(g) ightarrow C_2H_6(g)\n * **Halogenation**: Reaction with halogens (X_2)\n         ext{Ethene} + Br_2 ightarrow 1,2 ext{-dibromoethane}\n        C_2H_4(g) + Br_2(aq) ightarrow C_2H_4Br_2(aq)\n        *Observation*: Brown bromine water rapidly decolourises when mixed with unsaturated alkenes.\n * **Hydrohalogenation**: Reaction with hydrogen halides (HX)\n         ext{Ethene} + HBr ightarrow ext{Bromoethane}\n        C_2H_4(g) + HBr(g) ightarrow C_2H_5Br(l)\n * **Hydration**: Reaction with water under dilute acid catalyst (H^+)\n         ext{Ethene} + H_2O ightarrow ext{Ethanol}\n        C_2H_4(g) + H_2O(l) ightarrow C_2H_5OH(l)\n\n* **Substitution Reactions of Saturated Hydrocarbons**\n * **Mechanism**: Saturated alkanes do not undergo addition. Halogen substitution requires UV light catalyst to form free radicals.\n * **Cyclohexane vs Cyclohexene Investigation**:\n * *Cyclohexene* (Unsaturated): Undergoes rapid addition with bromine water without UV light, forming 1,2-dibromocyclohexane and decolourising solution.\n * *Cyclohexane* (Saturated): Does not react in dark. Under UV light, undergoes slow substitution forming 1-bromocyclohexane and hydrogen bromide (HBr):\n            C_6H_{12}(l) + Br_2(aq) ightarrow C_6H_{11}Br(l) + HBr(aq)\n\n## Properties, Reactions, and Production of Alcohols\n\n* **Properties and Homologous Series**\n * General Formula: C_nH_{2n+1}OH\n * Properties: Polar due to -OH group, forming intermolecular hydrogen bonds. High boiling points relative to alkanes. Soluble in water (solubility decreases as non-polar tail lengthens).\n * Combustion Enthalpy: Molar enthalpy of combustion increases in magnitude with increasing molecular mass.\n\n* **Chemical Reactions**\n * **Combustion**:\n * Complete: C_2H_5OH(l) + 3O_2(g) ightarrow 2CO_2(g) + 3H_2O(l)\n * Incomplete: Occurs under oxygen-deficient conditions producing CO(g)$or$C(s).\n * **Dehydration**: Heating with concentrated sulphuric acid (H_2SO_4$) catalyst at$180 ext{ }^ ext{o} ext{C}\n         ext{Alcohol} ightarrow ext{Alkene} + ext{Water}\n        C_2H_5OH(l) ightarrow C_2H_4(g) + H_2O(l)\n * **Substitution with HX**:\n         ext{Alcohol} + ext{Hydrogen Halide} ightarrow ext{Haloalkane} + ext{Water}\n        C_2H_5OH(aq) + HX(aq) ightarrow C_2H_5X(aq) + H_2O(l)\n * **Oxidation**:\n * *Primary Alcohols*: Partially oxidise to form Aldehydes; fully oxidise to form Carboxylic Acids.\n * *Secondary Alcohols*: Oxidise to form Ketones.\n * *Tertiary Alcohols*: Resistant to oxidation (no reaction).\n\n* **Industrial Production and Biofuels**\n * **Haloalkane Substitution**: C_2H_5X + OH^- ightarrow C_2H_5OH + X^-\n * **Fermentation of Glucose**:\n        C_6H_{12}O_6(aq) ightarrow 2C_2H_5OH(aq) + 2CO_2(g)\n        *Conditions*: Anaerobic environment, neutral pH, yeast enzyme catalyst, presence of nutrients, warm temperature ( ightleftharpoons 30 ext{ }^ ext{o} ext{C}$). Alcohol concentration capped at$ ightleftharpoons 14-15 ext{\%} (higher concentrations kill yeast, requiring distillation).\n * **Ethanol Fuel Assessment**:\n * *Advantages*: Renewable resource, reduces fossil fuel consumption, undergoes cleaner complete combustion, potential carbon-neutral pathway.\n * *Disadvantages*: Lower energy density (produces ightleftharpoons 66 ext{\%}$energy of petrol), arable land diverted from food crops, engine modification required for blends$>15 ext{\%}, engine corrosion due to moisture absorption.\n\n## Reactions of Organic Acids, Bases, Esters, and Surfactants\n\n* **Physical Properties Comparison**\n * **Carboxylic Acids**: Form strong hydrogen-bonded dimers. High boiling points and high water solubility (up to 4 carbons).\n * **Amines**: Basic compounds (pH > 7). Form hydrogen bonds. Boiling point increases with chain length.\n * **Amides**: High melting and boiling points (solids at room temperature due to extensive double hydrogen bonding networks).\n\n* **Esterification**\n * Reaction: Condensation reaction between alkanol and alkanoic acid under reflux using concentrated H_2SO_4 catalyst.\n         ext{Alkanol} + ext{Alkanoic Acid} ightleftharpoons ext{Alkyl Alkanoate (Ester)} + ext{Water}\n * Methanol + Hexanoic Acid ightarrow Methyl hexanoate + Water\n * Ethanol + Propanoic Acid ightarrow Ethyl propanoate + Water\n * Hexanol + Octanoic Acid ightarrow Hexyl octanoate + Water\n * Butanol + Propanoic Acid ightarrow Butyl propanoate + Water\n * *Reflux Mechanism*: Prevents loss of volatile organic reagents by condensing escaping vapors back into reaction vessel while allowing heating without pressure buildup.\n\n* **Soaps and Detergents**\n * **Structure**: Composed of long non-polar hydrophobic hydrocarbon tails and polar hydrophilic ionic heads (-COO^-Na^+).\n * **Mechanism**: Hydrophobic tails dissolve in non-polar grease/oil; hydrophilic heads interact with polar water. Agitation forms spherical **micelles** trapping oil inside, allowing grease to be dispersed and washed away in aqueous solution.\n\n## Polymers: Addition and Condensation\n\n* **Comparison of Major Polymer Types**\n * **Polyethylene (PE)**:\n * Structure: Addition polymer of ethene monomers (+CH_2-CH_2+_n).\n * Types:\n * *LDPE*: Branched chains, flexible, low density, low melting point ( ightleftharpoons 115 ext{ }^ ext{o} ext{C}). Uses: Plastic wrap, squeeze bottles, plastic bags.\n * *HDPE*: Unbranched linear chains, rigid, high density, higher melting point ( ightleftharpoons 135 ext{ }^ ext{o} ext{C}). Uses: Piping, buckets, wire insulation.\n * **Polyvinyl Chloride (PVC)**:\n * Structure: Addition polymer of chloroethene (+CH_2-CHCl+_n).\n * Properties: Rigid, flame-resistant, durable, water-resistant, low flexibility.\n * Uses: Electrical wire insulation, credit cards, water pipes, building fittings.\n * **Polystyrene (PS)**:\n * Structure: Addition polymer of styrene/phenylethene monomers (+CH_2-CH(C_6H_5)+_n).\n * Properties: Rigid due to bulky benzene rings, transparent, brittle, high thermal stability.\n * Uses: CD cases, foam cups, thermal insulation, tool handles.\n * **Polytetrafluoroethylene (PTFE / Teflon)**:\n * Structure: Addition polymer of tetrafluoroethylene (+CF_2-CF_2+_n).\n * Properties: Chemically inert, non-stick, high melting point, low friction coefficient, hydrophobic.\n * Uses: Non-stick cookware coatings, medical implants, electrical insulation.\n * **Nylon (Polyamide)**:\n * Structure: Condensation polymer formed between dicarboxylic acids and diamines (linked by amide bonds -CONH-).\n * Properties: High tensile strength, elastic, heat-resistant, durable.\n * Uses: Clothing, stockings, ropes, activewear.\n * **Polyester (PET)**:\n * Structure: Condensation polymer formed between dicarboxylic acids and diols (linked by ester bonds -COO-).\n * Properties: Hydrophobic, chemical-resistant, high tensile strength, wrinkle-resistant.\n * Uses: Drink bottles, synthetic fabrics, clothing.\n\n# Module 8: Applying Chemical Ideas\n\n## Analysis of Inorganic Substances\n\n* **Environmental Monitoring**\n * **Waterways**: Monitored for heavy metals (Pb^{2+}$,$Hg^{2+}) using Atomic Absorption Spectroscopy (AAS), and for acidity using pH meters to protect ecosystems.\n * **Atmosphere**: Monitored for oxides of sulphur (SO_x$) and nitrogen ($NO_x), which form acid rain:\n        SO_3(g) + H_2O(l) ightarrow H_2SO_4(aq)\n        2NO_2(g) + H_2O(l) ightarrow HNO_3(aq) + HNO_2(aq)\n * **Ozone Crisis**: Catalytic destruction of ozone (O_3) by Chlorofluorocarbons (CFCs) under UV radiation:\n         ext{Initiation: } CClF_3 + UV ightarrow Cl imes + CF_3 imes\n         ext{Propagation 1: } Cl imes + O_3 ightarrow ClO imes + O_2\n         ext{Propagation 2: } ClO imes + O imes ightarrow Cl imes + O_2\n         ext{Net Reaction: } O_3 + O imes ightarrow 2O_2\n\n* **Qualitative Identification Tests**\n * **Flame Tests for Cations**:\n * Barium (Ba^{2+}): Apple green flame\n * Calcium (Ca^{2+}): Brick red flame\n * Copper(II) (Cu^{2+}): Blue-green flame\n * Iron (Fe^{2+}/Fe^{3+}): Sparkly yellow flame\n * Lead (Pb^{2+}): White flame\n\n* **Quantitative Analytical Techniques**\n * **Colourimetry**: Measures light absorption of coloured solutions at specific wavelengths using excited state electron transitions.\n * **UV-Visible Spectrophotometry**: Quantifies ion concentrations by measuring light absorption in visible and ultraviolet spectra.\n * **Atomic Absorption Spectroscopy (AAS)**:\n * *Mechanism*: Sample aspirated into flame, hollow cathode lamp shines element-specific wavelength through vapor, detector measures light absorbance against calibration curve.\n * *Sensitivity*: Detects trace heavy metal concentrations down to parts per million (ppm) or parts per billion (ppb).\n * *Biological Applications*: Measures micronutrient trace elements (Zinc, Manganese, Copper, Cobalt, Magnesium) in soil and tissue samples.\n\n## Analysis of Organic Substances\n\n* **Qualitative Functional Group Tests**\n * **Carbon-Carbon Double Bond (C=C)**:\n * *Bromine Water Test*: Decolourises brown bromine water (Br_2(aq)).\n * *Baeyer's Test*: Decolourises purple alkaline potassium permanganate (KMnO_4).\n * **Hydroxyl Group (-OH)**:\n * *Active Metal Test*: Reaction with metallic Sodium (Na$) yields$H_2(g) bubbles.\n * *Ester Test*: Reflux with carboxylic acid produces sweet-smelling ester.\n * *Ceric Ammonium Nitrate Test*: Colour shift from yellow to red.\n * **Carboxylic Acid Group (-COOH)**:\n * *Litmus Test*: Turns blue litmus paper red.\n * *Sodium Bicarbonate Test*: Addition of NaHCO_3$effervesces$CO_2(g) gas.\n\n* **Instrumental Structural Analysis**\n * **Proton (^1H$) and Carbon-13 ($^{13}C) NMR Spectroscopy**:\n * Uses radiofrequency radiation in strong magnetic fields to flip nuclear spins between parallel and anti-parallel states.\n * Chemical shifts (\times in ppm) identify chemical environments of hydrogen and carbon atoms.\n * **Mass Spectroscopy**:\n * Sample ionised to positive radicals, accelerated through magnetic field, and deflected based on mass-to-charge ratio (m/z).\n * Identifies molecular mass and fragment structures.\n * **Infrared (IR) Spectroscopy**:\n * Measures absorption of infrared radiation causing molecular bond vibrations (stretching/bending).\n * *Characteristic Absorption Ranges*:\n * N-H$(amines):$3300 - 3500 ext{ cm}^{-1}\n * O-H$(alcohols):$3230 - 3550 ext{ cm}^{-1} (broad)\n * C-H$:$2850 - 3300 ext{ cm}^{-1}\n * O-H$(acids):$2500 - 3000 ext{ cm}^{-1} (very broad)\n * C=O$(carbonyl):$1680 - 1750 ext{ cm}^{-1}\n\n## Chemical Synthesis and Design\n\n* **Haber Process Case Study**\n * Equation: N_2(g) + 3H_2(g) ightleftharpoons 2NH_3(g)$, with$ imes H = -92 ext{ kJ }mol^{-1}\n * **Optimization Factors**:\n * *Stoichiometry*: 1:3$molar ratio of$N_2$to$H_2$. Continuous addition of reactants and condensation removal of liquid$NH_3\n * *Pressure*: Elevated to ightleftharpoons 200 ext{ atm}$to shift equilibrium right (4 moles gas$ ightarrow 2 moles gas) and increase reaction rate.\n * *Temperature*: Compromise temperature of ightleftharpoons 450 ext{ }^ ext{o} ext{C}$. Low temperature favors high equilibrium yield (exothermic), but higher temperature increases reaction rate.$450 ext{ }^ ext{o} ext{C}$balances rate and yield ($ ightleftharpoons 10-20 ext{\%} single-pass yield).\n * *Catalyst*: Magnetite (Fe_3O_4$) fused with$K_2O$,$Al_2O_3$, and$CaO$lowers activation energy$E_a.\n * **Social and Economic Impacts**: Provides essential nitrogen fertilizers sustaining global food supplies; historically enabled production of explosives during conflict.\n\n# Examination and Revision Strategies\n\n## Chemistry Study Techniques\n\n* **Weekly Summarisation**: Compile syllabus-aligned notes weekly to avoid content gaps.\n* **Structured Formatting**: Use comparison tables, color-coded equation lists, and annotated flowcharts to consolidate memory retention.\n* **Active Recall Worksheets**: Create fill-in-the-blank practice sheets for equations, definitions, and mechanisms.\n* **Past Paper Practice**: Complete full HSC past papers under timed conditions.\n\n## Common Examination Pitfalls and Solutions\n\n* **Units**: Always append correct physical units (e.g., kJ ext{ }mol^{-1}$,$g ext{ }L^{-1}$,$mol ext{ }L^{-1}).\n* **Significant Figures**: Final answers must match the lowest number of significant figures provided in the numerical prompt data.\n* **Chemical Detail**: Integrate balanced chemical equations, standard states, and structural diagrams into all extended text responses.\n* **Response Formatting**: Structure extended responses using clear subheadings, comparison tables, and boxed flowcharts.\n\n## HSC Chemistry Mark Alignment and Scaling\n\n* **Mark Alignment Data Example**:\n * Raw Mark 91/100 ightarrow Aligned HSC Mark 96/100\n * Raw Mark 87/100 ightarrow Aligned HSC Mark 93/100\n * Raw Mark 68/100 ightarrow Aligned HSC Mark 82/100\n* **Scaling Comparisons (Scaled Mark out of 50 vs HSC Mark)**:\n * Chemistry: HSC 49.5/50 ightarrow$Scaled 50.0; HSC 45.0/50$ ightarrow$Scaled 43.1; HSC 34.5/50$ ightarrow Scaled 25.2.\n * English Advanced: HSC 49.5/50 ightarrow$Scaled 50.0; HSC 45.5/50$ ightarrow$Scaled 42.3; HSC 38.0/50$ ightarrow Scaled 27.0.\n * Mathematics: HSC 50.0/50 ightarrow$Scaled 50.0; HSC 46.5/50$ ightarrow$Scaled 42.9; HSC 36.5/50$ ightarrow$$ Scaled 25.5.