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

Amine

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