S1 Intro to IB HL Chemistry

Element

a substance that cannot be broken down by chemical means into smaller substances

Compound

2 or more element chemically bonded together and can be seperated through chemical means

Mixture

2 or more substance not chemically bonded together and can be seperated through physical means

Two types of mixture

Homogenous: uniform 
Heterogenous: non-uniform

Filtration

used to seperate insolube solid (residue) from filtrate

Distillation

seperate liquids with different melting point
- lower melting point vapourises first then condenses into liquid

Recrystalisation

Purify solid by dissolving in hot solvent (Solid → Liquid)

Crystalisation

Making pure crystals from impure liquids (Liquid → Solid)

Chromatography

seperate mixture of soluble substances e.g Ink

Kinetic Molecular Theory

Solid: Vibrate in fixed position, Fixed Volume 
Liquid: Slide past each other, Fixed Volume
Gas: Move freely, Dynamic volume

Kelvin

Measure the kinetic energy of particle
K = C + 273

Deposition

Gas → Solid

Sublimation

Solid → Gas

Atomic number (Z)

number of proton in the nucleus

Atomic mass (A)

Proton + Neutron = Mass

Mass of electron

1/1836

Isotopes

atom of the same element with the same atomic number but different mass (Neutron)

Relative atomic mass formula

A = (% of first mass) + (% of 2nd mass)… / 100

Mass spectrometer

used to determine the relative atomic mass & identifying isotopes

Steps to identify isotopes

1. Ionisation: Turn into ions

2. Acceleration: Put into same electric field → Same kinetic energy

3. Deflection: Deflected by magnetic field

4. Detection: Hit detector, strength signal isotope abundance

5. Data analysis: Produce mass spectrum (peaks for isotopes) showing relative atomic mass & Isotopes abundance

Mass vs Charge

Charge increase → Deflection increase (Direct)
Mass Increase → Deflection decrease (Indirect)

Bohr theory

Energy level are fixed, spherical & orbitual

• Occupy from the lowest level (Near nucleus) first

Electromagnetic spectrum (Decreasing Wavelength and Increasing frequency)

Radio waves, microwaves, infrared, visible light, ultraviolet, X rays, Gamma rays

Energy

High frequency = High energy

Emission spectra

1. Ground state: Electron in lowest energy level

2. Absorption: Photon (energy) absorbed → electron move to high energy level (Excited state - Unstable)

3. Emission: Electron fall to lower energy level emitting Photon (energy)

Convergence limit

Occur at high energy because…

• energy level closer together

• Ionisation is the highest (at n infinity, outermost)

Frequency

f = speed of light ( c) / wavelength

Energy of photon

P = Planck Constant (h) (6.626×10^(34)) x f

Energy

E = Avogadro number (n) x P

usually in Joules

J to Kj

Kj = J / 1000

Hydrogen emission spectrum

Energy level

Divided into sublevels (s,p,d,f) depends on orbitual (High % of finding e)

s sublevel

max 2 electron, spherical shaped

p sublevel

max 6 electron (3 orbitual), dumbell shaped

d sublevel

max 10 electron, 5 orbitual

f sublevel

max 14 e, 7 orbitual

Electron configuration

1s², Energy level, sub level, number of electron

Degenerate orbitual

or bitual within the same sub level of an atom → same energy

d-block element

4s fills first before 3d sublevel
Exception: Cr & Cu

Orbitual diagram

visual reperesentation of electron configuration 

Ionisation

The process of removing e from atom in ground state

Repulsion

force that push particle with same charge away (electrons in shells)

Successive ionisation energies

process of removing electron from atoms, start from higher energy sublevel first

Avogadro constant (n)

6.02 × 10^(23)

1 = 1 moles

Formula unit

simplest ratio of ions in compound 

→ convert before finding moles 

Moles (n)

n = mass (m) / Molar mass (M)

Number of _ (atom/electron):

N = n x avogadro constant

Percentage composition

1. convert to mass

2. convert to mole

3. equal ratio

Moles (n) in liquid

n = concentration ( c ) x volume (dm³) V

Avogadro law

equal volume of GAS at the same temperature and pressure will have the same number of gas particles

Ideal gases properties

• particles are constant (small size), random and move in a straight line motion

• weak intermolecular forces between particles

• distance between particles > size of particles

• Average kinetic energy directly proportional to absolute temperature (Kelvin)
  → Ideal condition: Low pressure and high temperature 

Real gas

Deviation from the Ideal gas model due to…
→ High pressure and low temperature

→ slower speed → attraction between particles

→ Liquidified

→ higher molar mass

Standard condition (STP)

273 K (0 C) & 100kPa

Moles in gas

n = V / 22.7 dm^-3 mol-1 (Molar volume)

Constant temperature

Pressure and volume are inversely proportional

P1V1 = P2V2

Constant pressure

Volume of ideal gas directly proportional to absolute temperature (K)

V1/T1 = V2/T2

Constant volume

Pressure of fixed mass directly proportional to absolute temperature (K)

P1/T1 = P2/T2

Combined laws

PV = nRT

P1V1 / T1 = P2V2/T2

Molar mass

M = mRT / PV