Ficha de revisão: Chemistry Revision Map

📋 Course Outline

1. Acids Bases and Titrations
2. Redox and Electrochemistry
3. Equilibrium and Le Chatelier
4. Organic Functional Groups
5. Organic Reactions and Isomers
6. Spectroscopy and Mass Spectrometry
7. Amino Acids and Intermolecular Forces
8. Fuel Cells and Green Chemistry
9. Calculations and Written Responses

📖 1. Acids Bases and Titrations

📝 Essential Points

📌 A strong acid dissociates completely, whereas a weak acid establishes an equilibrium represented by ⇌.

• A monoprotic acid can donate one H⁺, whereas a diprotic acid can donate two H⁺ ions.

📐 Formula — The acid dissociation constant is $K_a=\frac{[H^+][A^-]}{[HA]}$ and the acidity is $pK_a=-\log K_a$.

📐 Formula — The relationships for amount, concentration, dilution, and conjugate pairs are $n=cV$, $c=\frac{n}{V}$, $c_1V_1=c_2V_2$, and $pK_a+pK_b=14$.

• At the equivalence point of a 1:

  • 1 titration
  • the amount of acid equals the amount of base
  • volumes must be expressed in litres

• A strong acid–strong base titration has equivalence pH 7, a weak acid–strong base titration has equivalence pH above 7, and a strong acid–weak base titration has equivalence pH below 7.

💡 Memory Hook

Identify → calculate → titrate

📖 2. Redox and Electrochemistry

📝 Essential Points

• Oxidation occurs at the anode and reduction occurs at the cathode; oxidation loses electrons and reduction gains electrons.

• In a galvanic cell, the anode is negative and produces electrons, while the cathode is positive and uses electrons.

• Electrons flow from the anode to the cathode in a galvanic cell, while salt-bridge anions migrate to the anode and cations migrate to the cathode.

• During electrolysis of molten NaCl, Na⁺ is reduced to sodium at the cathode and chloride ions are oxidised to chlorine at the anode.

💡 Memory Hook

AN OX, RED CAT

📖 3. Equilibrium and Le Chatelier

📝 Essential Points

• Adding a reactant shifts equilibrium toward products, whereas adding a product shifts equilibrium toward reactants.

• Increasing pressure shifts a gaseous equilibrium toward fewer gas particles, while decreasing pressure shifts it toward more gas particles.

• Increasing temperature favours the endothermic direction, whereas decreasing temperature favours the exothermic direction.

📐 Formula — The equilibrium constant is expressed as $K_c=\frac{[products]^{coefficients}}{[reactants]^{coefficients}}$; $K_c>1$ indicates products are favoured and $K_c<1$ indicates reactants are favoured.

💡 Memory Hook

Change conditions → equilibrium shift

📖 4. Organic Functional Groups

📝 Essential Points

• The functional groups C=C, C≡C, –OH, –CHO, >C=O, –COOH, –COO–, –NH₂, and –C≡N are respectively alkene, alkyne, alcohol, aldehyde, ketone, carboxylic acid, ester, amine, and nitrile.

• An alkene reacts with bromine by addition across the C=C bond.

📖 5. Organic Reactions and Isomers

🔑 Key Concepts & Definitions

• Ester : Contains the functional group R–COO–R.

📝 Essential Points

• A primary alcohol can oxidise to an aldehyde and then to a carboxylic acid, whereas a secondary alcohol oxidises to a ketone.

• Reduction of a nitrile produces an amine.

📌 Structural isomers have the same molecular formula but different connectivity, whereas E/Z isomers have a C=C bond with different groups on both carbons and differ in spatial arrangement.

💡 Memory Hook

Alcohol → aldehyde → carboxylic acid

📖 6. Spectroscopy and Mass Spectrometry

📝 Essential Points

• IR absorptions at 3200–3600 cm⁻¹ broad, 2500–3000 cm⁻¹ very broad, approximately 1700 cm⁻¹ strong, 1600–1680 cm⁻¹, and 2850–3100 cm⁻¹ identify alcohol O–H, carboxylic-acid O–H, C=O, C=C, and C–H respectively.

• A strong approximately 1700 cm⁻¹ peak with a very broad 2500–3000 cm⁻¹ peak indicates a carboxylic acid, while a 1700 cm⁻¹ peak without O–H indicates an aldehyde or ketone.

• The highest molecular peak in a mass spectrum is the molecular ion M⁺.

📖 7. Amino Acids and Intermolecular Forces

📝 Essential Points

📌 An amino acid is positive when pH<pI, neutral when pH=pI, and negative when pH>pI.

• During electrophoresis, positive ions move toward the negative electrode and negative ions move toward the positive electrode.

• The relative strength of intermolecular forces is hydrogen bonding greater than dipole–dipole forces greater than dispersion forces.

• OH, COOH, and NH₂ groups increase solubility through hydrogen bonding with water, while longer hydrocarbon chains lower solubility.

📖 8. Fuel Cells and Green Chemistry

📝 Essential Points

📌 In an acidic hydrogen fuel cell, H⁺ moves to the cathode, whereas in an alkaline hydrogen fuel cell, OH⁻ moves to the anode.

• Electrons travel through the external circuit and ions travel through the electrolyte in a hydrogen fuel cell.

📐 Formula — Atom economy is calculated as $AE=\frac{M_r(\text{desired product})}{M_r(\text{all reactants})}\times100$, and a higher atom economy is better.

📐 Formula — The E-factor is calculated as $E=\frac{\text{waste}}{\text{product}}$, and a lower E-factor is better.

💡 Memory Hook

Higher atom economy, lower E-factor

📖 9. Calculations and Written Responses

📝 Essential Points

📐 Formula — Use $n=cV$ for moles, $c=\frac{n}{V}$ for concentration, $c_1V_1=c_2V_2$ for dilution, $pH=-\log[H^+]$ for pH, and $pK_a=-\log K_a$ for pKa.

• For Calculate questions, write the formula, substitute values, and give the answer with units.

• Justify responses should contain a claim, relevant data, and chemical reasoning.

• A two-mark short response requires an answer and a reason, while a three-mark response requires a prediction, chemical reason, and evidence or data.

💡 Memory Hook

Formula → substitution → answer with units

📊 Synthesis Tables

Titration Equivalence pH

Titration	Equivalence pH	Indicator condition
Strong acid + strong base	7	Indicator range overlaps pH 7
Weak acid + strong base	>7	Indicator range overlaps pH above 7
Strong acid + weak base	<7	Indicator range overlaps pH below 7