chem - absolutely need to know

Ammonium

NH₄⁺

Nitrate

NO₃^-

Hydrogen carbonate

HCO₃^-

Carbonate

CO₃^2-

Sulfate

SO₄^2-

Phosphate

PO₄^3-

Silver

Ag⁺

Zinc

Zn²⁺

Ionic bonding

The electrostatic attraction between oppositely charged ions

Covalent bonding

The electrostatic attraction between a shared pair of electrons and two positively charged nuclei.

Diamond: bonding & properties

(sp³): each C tetrahedrally bonded to 4 C

• giant 3D network → extremely hard, very high mp

• electrical insulator

• thermally conductive

• insoluble

Graphite: bonding & properties

(sp²): layers of hexagonal sheets

• within a sheet strong σ + delocalized π

• weak forces btw sheets → layers slide (lubricant)

• conducts electricity/heat btw layers - comes from structure (delocalised e-s can move btw layers), if not solid: can’t conduct

• opaque, soft

Graphene: bonding & properties

Single graphite layer

• exceptional electrical/thermal conductivity

• very strong yet flexible

• high SA

Fullerenes (C₆₀): bonding & properties

simple molecular solid → lower mp, soluble in nonpolar solvents, semiconducting behavior.

Silicon & Silicon dioxide: bonding & properties

Silicon (sp³ network). Silicon dioxide (SiO₂).

Both: giant covalent lattices; high mp/hard;

Si: semiconductor (temperature-dependent conductivity);

SiO₂ is an electrical insulator, hard, insoluble; tetrahedral Si–O–Si network.

Sigma bond

Head-on overlap along the internuclear axis.

Can form from overlap btw:

• s-s

• s-p

• p-p

• hybrid-hybrid

Pi bond

Side-on overlap of unhybridised p-orbitals, electron density is above and below internuclear axis. (p-p)

Electronegativity difference & respective bond types

0: pure covalent

0 - 0.4: non-polar covalent

0.4 - 1.7: polar covalent

> 1.7: ionic

Formal charge equation

FC = (valence electrons) - ½(bonding electrons) - (non-bonding electrons)

Electrically conductive metals - trends & top 3

The larger the n of delocalised e-s → the more electrically conductive

1. Ag - silver

2. Cu - copper (cost + conductivity)

3. Au - gold

Group 1: reactivity trend down group

• Increases

More shells → outer e-s further from nucleus & more shielding → weaker attraction → easier to lose e-s

Group 17: reactivity trend down group

• Decreases

more shells → electrons further & increased shielding → weaker electron attraction → less ability to gain electrons

What is an ester linkage and how is it formed?

-COO-

Condensation reaction (loss water) btw carboxylic acid + alcohol

What is an amide linkage and how is it formed?

-CONH-

Condensation reaction btw carboxylic acid + amine

Electron domains & their respective bond angles and molecular geometries (no lone pairs)

• 2: 180° - linear

• 3: 120° - trigonal planar

• 4: 109.5° - tetrahedral

• 5: x3 120° + x2 90° - trigonal bipyramidal

• 6: 90° - octahedral

Aldehyde - structure & suffix

-CHO

-al

Ketone - structure & suffix

–C(=O)–

-one

Ester - structure & suffix

–COO–

-anoate

Amine - structure & suffix

–NH₂

-amine

Amine vs amide (formula)

amine: –NH₂

amide: –CONH₂

Amide - structure & suffix

–CONH₂

-amide

Ester vs ether (formula & suffix)

Ester: -COO -anoate

Ether: -O- -oxy-

Ether - structure & suffix

–O–

-oxy-

Nitrile - structure & suffix

–C≡N

-nitrile

Acyl chloride - structure & suffix

–COCl

-anoyl chloride

What is the carbonyl group and is it a functional group?

C=O

It's not a functional group on its own — it's a structural feature that appears inside several functional groups

Standard enthalpy change of atomisation

The enthalpy change when 1 mole of gaseous atoms is formed from an element under standard conditions.

x element → 1 atom (g)

Ionisation energy

The enthalpy change when one electron is removed from each atom in 1 mole of gaseous atoms under STP

Electron affinity

The enthalpy change when 1 electron is added to each atom in 1 mole of gaseous atoms under STP

Lattice enthalpy

The enthalpy change when 1 mole of an ionic compound is broken apart into its constituent gaseous ions under STP

Formula for oxidation - eg. iron

Fe → Fe²⁺ + 2e^-

(electrons on the products side - because electrons are lost)

Formula for reduction - eg. iron

Fe²⁺ + 2e^- → Fe

(electrons on the reactants side - because electrons are gained)

Does ΔG^ᶿ have to be positive or negative for a reaction to be spontaneous?

Negative

Reasons for less than 100% percentage yield (4)

• Side reactions

The reactants don't only react with each other, but they also undergo other reactions simultaneously, producing different products. Those byproducts "use up" some of your reactants, so less of the intended product is made → actual yield drops.

• Incomplete reaction

Some reactants remain unreacted, so you get less product than theoretically possible.

• Loss on transfer/purification

Physical losses during the experiment: pouring a liquid between containers, filter a solid, or purify your product, small amounts stick to glassware, filter paper, or are lost in the process. Not all products collected.

• Impure reagents

Starting materials contain impurities: actual amount of reactive substance is less than you think: you have fewer moles than you assumed → theoretical yield was overestimated → actual yield is lower than expected

Reasons for less than 100% percentage yield

• Wet/impure product

• Solvent trapped

Solvent molecules from the reaction mixture get trapped in or on the product and aren't fully removed during drying.

• Calibration errors

Your measuring equipment (balance, thermometer, volumetric glassware) isn't accurate — it consistently reads higher than the true value.

What does atom economy measure? (formula in data booklet)

It measures how much of the mass of your reactants ends up in the desired product versus being wasted as byproducts.

How efficient a reaction is in terms of atoms - it is a property of the reaction itself, not your technique.

• High atom economy: most atoms end up in the product → less waste

• Low atom economy: lots of atoms end up in byproducts → more waste

Why does atom economy matter?

Evaluate reactions from an environmental and economic perspective:

• Low atom economy = more waste to dispose of = more costly and polluting

• Industry prefers high atom economy reactions to reduce waste, cost, and environmental impact

Green chemistry principles: designing reactions that minimise waste at the molecular level

Equation for rate of reaction - units

Rate of reaction = | change concentration | / change time

Units: mol dm^-3 s^-1

Overall rate of reaction equation

2A + 2B → (1) C

overall rate: rate(A)/2 = rate(B)/2 = rate(C)/(1)

Divide rate by coefficient