QCE Chem Flashcards + Questions 2026 syllabus

Linear shape

Bent shape

104 degree bond angle

Trigonal planar shape

120 degree bond angle

Tetrahedral shape

109 degree bond angle

Trigonal pyramidal shape

107 degree bond angle

Emission spectrum

Show white lines for emitted light

Absorption spectrum

Rainbow of absorbed light

Electronegativity difference of polar bonds

0.5-1.7 electronegativity difference

Electronegativity difference of non-polar bonds

<0.5 electronegativity difference

2 outer atoms, 1 inner atom

Linear

3 outer atoms, 1 inner atom

Trigonal Planar

4 outer atoms, 1 inner atom

Tetrahedral

3 outer atoms, 1 inner atom, 1 lone pair

Trigonal Pyramidal

2 outer atoms, 1 inner atom with lone pair

Bent

Metals which replace hydrogen in acid and water

Magnesium to potassium

Metals which replace hydrogen in acid only

Lead to aluminium

Metals which don’t replace hydrogen

Platinum to antimony

What is the oxidation number of hydrogen in metal hydrides?

-1

In compounds with nonmetals, what is the oxidation number of hydrogen?

+1

How to balance half-equations

• Write the skeleton redox half equations

• Balance all elements but oxygen and hydrogen

• Balance oxygen with H2O, then balance hydrogen with H+

• Balance charges with electrons

• Multiply each half-equation by a number for an equal amount of electrons

Parts of a galvanic cell

Anode, cathode, electrolyte, external circuit, salt bridge

Electron flow in galvanic cell

Negative anode to positive cathode

Purpose of salt bridge in galvanic cells

Prevents buildup of charges, keeping the electrodes balanced

Parts of an electrolytic cell

Negative cathode, positive anode, porous barrier, electrolyte, voltage

Redox reaction

Transfer of electrons between chemical species

Low on SEP table

Strong oxidising agent, likely to reduce

High on SEP table

Strong reducing agent, likely to oxidise

Why electrode polarity changes in electrolytic cells

• Reduction is always at the cathode

• Reduction is electron gain, must be at the half-cell gaining electrons

Therefore the cathode always gains electrons

• in galvanic cells, electrons spontaneously flow to positive electrode, so cathode is positive in galvanic cells

• in electrolytic cells, electrons artificially flow to negative electrode, so cathode is negative in electrolytic cells

Alkanes

No functional group

Alkenes

Double carbon bond, no true functional group

Alkynes

Triple carbon bond, no true functional group

Alcohols

Hydroxyl OH

Aldehydes

Terminal carbonyl (double-bonded oxygen)

Ketones

Non-terminal carbonyl (double-bonded oxygen)

Carboxylic acids

terminal carboxyl group (carbonyl + hydroxyl)

-oic acid

Haloalkanes

Alkane with halogen in place of hydrogen

Rules of branched molecules

• longest continuous chain is parent chain

• Name: (position of branches)(name of branches)(parent chain)

• order of carbons starts from the end the functional group is closest to. double/triple bonds are functional groups, branches are not

Nomenclature rule

hyphenate between letters and numbers, use comma between numbers

OH

hydroxyl

Double-bonded O

carbonyl

carboxyl group

Ester

Ester functional group (double-bonded O, O in middle)

Product of alcohol and carboxylic acid

Alcohol-yl acid-ate

Ester

Amines

Amino functional group (NH2)

Amino group

Name this molecule

N,N-dimethylmethanamine (amine)

Name this molecule

butyl pentanoate (ester)

Amide group

Amide

Amide functional group (carbonyl + amino)

Name this molecule

N-methyl-N-propylethanamide

Name this molecule

3-ethyl-2-methylpentane

Name this molecule

2,3-dimethylbutane

Name this molecule

2,2-dimethylpropane

Name this molecule

4-methylpent-2-ene

Name this molecule

3-methylbutan-2-ol

Primary Alcohols

Carbon with hydroxyl is bonded to one other carbon

Secondary Alcohols

Carbon with hydroxyl is bonded to two other carbons

Tertiary Alcohols

Carbon with hydroxyl is bonded to three other carbons

Primary Haloalkane

Carbon with halogen is bonded to one other carbon

Secondary Haloalkane

Carbon with halogen is bonded to two other carbons

Tertiary Haloalkane

Carbon with halogen is bonded to three other carbons

Functional group

Atom/group of atoms that impacts reactivity of a molecule

Class

Group of compounds with same functional group

Homologous series

Group of compounds with same functional group and general formula

Successive members differ by CH2

Isomers

Compounds with same molecular formula but different arrangement

Structural isomer

Atoms connected in a different order, different structural formula and name

Functional group isomers

Changed functional group e.g. ketone vs aldehyde

Positional isomers

Changed position of functional group e.g. propan-1-ol vs propal-2-ol

Chain length isomers

Changed main chain length, straight chain vs single or multiple branches off a parent chain

Stereoisomers

Atoms connected in the same order, different arrangement in 3D space

Geometric isomers

Occur when rotation in a molecule is restricted somewhere (e.g. due to double bonds). Cis or trans

Cis isomers

Particular atoms attached to carbons are on the same side

Trans isomers

Particular atoms attached to carbons are on the opposite side

Optical isomers

Same molecular/structural formulas, in 3D space are mirror images of each other.

Chiral carbon / chiral centre

Carbon with 4 different groups attached

Chirality

Two objects that are mirror images of each other and cannot be superimposed

Enantiomers

Pair of chiral molecules. Identical physical properties (except optically), but interact differently with other chiral molecules

Intermolecular forces

Forces between molecules

Dispersion force

• Weakest intermolecular force

• affects all molecules

• temporary due to movement of electrons

• increases with molecular mass

Dipole-dipole force

• stronger than dispersion force

• affect polar molecules

• positive and negative nodes of two molecules

• fixed

Hydrogen bonding

• a type of dipole-dipole force

• strongest intermolecular force

• between a positive H and a lone electron pair on a N, O, or F on another molecule

• fixed

Intermolecular forces of alkanes and alkenes

non-polar, only have dispersion forces

Intermolecular forces of alcohols

• polar

• dispersion forces

• due to hydroxyl, hydrogen bonding (as acceptor and donor)

Intermolecular forces of carboxylic acids

• polar

• dispersion forces

• due to hydroxyl, hydrogen bonding (as acceptor and donor)

• due to carbonyl, hydrogen bonding (donor only)

Volatility

qualitative measure of how easily a substance changes from liquid to gas

Correlation between boiling point and intermolecular force strength

As intermolecular strength increases, boiling point increases

Correlation between molecular mass and boiling point

As carbon chain length/molecular mass increases, boiling point increases

Correlation between surface area and boiling point

• As surface area increases, boiling point increases

• Branched molecules have weaker intermolecular forces

Correlation between functional group and boiling point

Different functional groups have different intermolecular forces

How to answer an intermolecular force question

• structure of molecules

• intermolecular forces present in each molecule

• which molecular has stronger intermolecular forces and why

• answer

Polarity and solubility

• Polarity of each molecule due to functional groups affects solubility

• more polar groups a molecule has, the more polar it is and the more soluble it is in polar solvent

Carbon chain length and solubility

• as chain length increases, the non-polar portion of the molecule increases → solubility in polar solvent decreases

• non-polar regions up to 4 carbons are negligible

Alkane + Oxygen

Oxidation (combustion): → Carbon dioxide + Water

Alkane + Halogen under UV light

Substitution: → Haloalkane + Hydrogen halide

Haloalkane + Halogen under UV light

Substitution: → Dihaloalkane + Hydrogen Halide

Haloalkane + Ammonia with heat and ethanol

Substitution: → Amine + hydrogen halide

Haloalkane + dilute sodium hydroxide

Substitution: → Alcohol + Sodium halide

Haloalkane + concentrated sodium hydroxide under heat

Elimination: → Alkene + Sodium halide + Water

Alkene + Halogen

Addition (halogenation): → Dihaloalkane

Alkene + Hydrogen Halide

Addition (hydrohalogenation): → Haloalkane