chemistry

Boyle’s Law

Boyle’s Law

Pressure is inversely related to volume

P₁V₁ = P₂V₂

Vice President is a Boy

Charles’s Law

Temperature is directly proportional to volume

V₁/T₁ = V₂/T₂

Charlie and the chocolate factory on TV

Gay Lussac’s Law

Pressure is directly proportional to temperature

P₁/T₁ = P₂/T₂

Personal Trainer is Gay

Avogadro’s Law

Volume is directly proportional to the amount of gas (moles)

Equal volumes of all gases, at the same temperature and pressure, have the same number of molecules

Thompson’s Plum Pudding Model (1904)

Negatively charged electrons are embedded within the uniform, positively charged atom

Rutherford’s Gold Foil Experiment

Bombardment of gold foil with alpha particles showed that only some particles were deflected, most passed straight through

Rutherford’s Nuclear Model (1911)

Dense, small, positively charged nucleus with electrons orbiting like planets in individual orbits

Mostly empty space

Bohr Model (1913)

Electrons orbit the nucleus in fixed energy levels

Various energy levels can hold different numbers of electrons

Ground state and excited state electrons

Only explains emission spectra for hydrogen atom

Schrödinger Quantum Mechanical Model (1926)

Assumes the electron is a wave and describes the regions in space, called orbitals, where electrons are most likely to be found

Concept of sub-energy levels

Law of Conservation

Energy is not created nor destroyed, only transferred from one form to another. The total energy of an isolated system remains constant.

Law of Disorder

The entropy of a closed system is always increasing. A reaction will be spontaneous if the products are of higher entropy than the reactants because particles have a tendency to move towards a state of higher disorder and lower energy.

Collision theory

The rate of a chemical reaction increases as the frequency of successful collisions between reactant particles increases. For a successful collision to occur, particles collide with sufficient energy to overcome activation energy and in proper orientation.

Indigenous practices - Cycads

Cycad fruits contain the toxic substance cycasin

Causes vomiting, nausea, and abdominal pains, as well as long-term damage to the nervous system and liver

Very low solubility in water

Cooked → Grated/powdered (increase SA) → Leached

Alpha radiation

Good ionising radiation

Stopped by paper (low penetrating power)

Beta radiation

Fair ionising radiation

Stopped by aluminium foil

Occurs with surplus neutrons

Gamma radiation

Electromagnetic radiation: no particle - high energy & high frequency

Low ionising radiation

Stopped by lead (high penetrating power)

Positron emission (β+)

Occurs with surplus protons

Limewater test

Limewater will turn cloudy in the presence of carbon dioxide gas

CO_2(g) + Ca(OH)_2(aq) → CaCO_3(s) + H₂O_(l)

Pop test

In the presence of hydrogen gas, a burning splint will be put out with a ‘pop’ sound

H_2(g) + 2O_2(g) → H₂O_(l)

Glowing splint test

In the presence of oxygen gas, a smouldering splint will reignite

Oxygen is a key component in combustion → rate of combustion increases in an abundance of oxygen

Solubility rules

Activity series

Isotopes in medicine - Iodine-123

Half-life of 13.22 hours

Used in medical imaging to detect thyroid function and detect adrenal dysfunction

Produced from a cyclotron

Isotopes in Industry - Cobalt-60

High intensity gamma ray emitter - can take industrial x-rays of welding seams to detect flaws in structures

Isotopes in Agriculture - Phosphorus-32

Used in fertilisers to track a plant’s intake of fertiliser from the roots to the leaves, as phosphorus emits beta radiation that can be mapped

Hund’s law

Electrons are placed in individual orbitals in a subshell before doubling up in the same orbital

Pauli’s Exclusion Principle

No more than 2 electrons can occupy the same orbital, two electrons in the same orbital must have opposite spin

Aufbau Principle

Electrons fill orbitals starting at the lowest available energy state before filling in higher states

Properties of an ideal gas

• Compressible

• Takes shape of container

• Always in motion

• Collides elastically with container - no energy loss

• Intermolecular forces between particles assumed to be zero

Physical properties of Ionic Compounds

• Hard - strong, rigid ionic bonds

• High m.p, b.p

• Brittle - applying pressure shifts alignment of ions that are in a lattice structure

• Poor conductors of electricity and heat (solid) - lack of mobile charge carriers as ions are in rigid lattice structure

• Good conductors of electricity and heat (aqueous) - ions are free to move

• Soluble - in polar solvents (e.g. water), where ion-dipole attraction results in ions of solute being surrounded by molecules of solvent

Physical Properties of Metals

• Hard and dense - strength determined by number of valence electrons

• Malleable, ductile - metal ions are free to move over each other while maintaining their metallic bonds

• Good conductors of electricity and heat - delocalised electrons as mobile charge carriers

• Lustrous - delocalised electrons reflect light well

Physical Properties of Covalent Network Substances

• Insulators - atoms are neutral and held by strong covalent bonds, electrons are not free to move

• Hard and strong - covalent bonds are strong

• High m.p and b.p - all covalent bonds need to be broken

• Insoluble - polar solvents like water are not attracted to the neutral atoms of a covalent network substance

Physical Properties of Covalent Molecular Substances

• Soft and flexible - weak intermolecular forces

• Relatively low m.p and b.p - weak intermolecular forces

• Many are insoluble, however polar covalent molecular substances (e.g. water) dissolve well in a polar solvent

• Do not conduct electricity (aqueous) - dissolve into molecules rather than ions

Indicators of a chemical reaction

• Permanent colour change

• Formation of a precipitate

• Formation of a gas (effervescence)

• Production of an odour

• Change in temperature

• Burning

• Production of light

Haber process

Heterogenous catalyst, reversible reaction

Atmospheric nitrogen to ammonia, catalyst of finely divided iron which breaks triple bond of nitrogen

2N_2(g) + 3H_2(g) 2NH_3(g)

Elephant toothpaste

Homogenous catalyst

Possible catalysts:

• Saturated KI_(aq)

• Yeast

• KMnO₄

• MnO₂

2H₂O_2(aq) 2H₂O_(l) + O_2(g)

Contact process

Multi-step process of producing sulfuric acid

1. Make sulfur dioxide

   S_(s)+O_2(g) SO_2(g)

2. Convert sulfur dioxide → sulfur trioxide via heterogenous vanadium pentoxide catalyst

   2SO_2(g)+O_2(g) 2SO_3(g)

3. Convert sulfur trioxide → concentrated sulfuric acid

   H₂SO_4(l)+SO_3(g)→H₂S₂O_7(l) - (oleum)

   H₂S₂O_7(l)+H₂O_(l)→2H₂SO_4(l)