Chemistry Paper 2 Comprehensive Revision Notes

Atomic Structure and the Periodic Table

• Subatomic Particle Properties and Charges:

  • Atoms are composed of protons, neutrons, and electrons.

  • Protons have a relative charge of $+1$.

  • Neutrons have a relative charge of $0$.

  • Electrons have a relative charge of $-1$.

• Isotopes:

  • Defined as atoms of the same element that contain different numbers of neutrons.

• Periodic Table Organization:

  • Group number indicates the number of outer electrons.

  • Period number indicates the total number of electron shells.

Chemical Bonding

• Ionic Bonding:

  • Occurs between a metal and a non-metal.

  • Involves the transfer of electrons.

• Covalent Bonding:

  • Occurs between 2 non-metals.

  • Involves the sharing of electrons.

• Metallic Bonding:

  • Characterized by a lattice of positive ions surrounded by delocalised electrons.

Acids, Bases, and Salts

• pH Scale Definitions:

  • Acid: $\text{pH} < 7$

  • Base: $\text{pH} > 7$

  • Neutral: $\text{pH} = 7$

• Neutralisation Reaction:

  • $\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}$

• Soluble Salts Preparation Methods:

  • Titration method

  • Excess base method

The Mole and Calculations

• Mole Calculation Formula:

  • $\text{Mole} = \frac{\text{mass}}{M_r}$

• Relative Formula Mass ($M_r$):

  • Defined as the sum of atomic masses taken from the periodic table.

• Reacting Mass Calculations:

  • Requires using the mole ratio derived from a balanced chemical equation.

Electrolysis

• Core Definition:

  • The breakdown of a substance using electricity.

• Electrodes and Mnemonic:

  • Anode = positive electrode ($+$)

  • Cathode = negative electrode ($-$-)

  • Mnemonic device: PANIC (Positive Anode, Negative Is Cathode)

• Electrolyte Condition:

  • The electrolyte must be either molten or in solution.

Rates of Reaction

• Factors that Increase the Rate of Reaction:

  • Higher temperature

  • More concentration

  • More surface area

  • Addition of a catalyst

• Methods of Measurement:

  • Gas volume

  • Loss of mass

  • Color change

Energy Changes

• Exothermic Reactions:

  • Gives out heat energy, resulting in a temperature rise.

• Endothermic Reactions:

  • Takes in heat energy, resulting in a temperature drop.

• Reaction Energy Profiles:

  • Energy profile diagrams show energy changes throughout the course of a reaction.

Tests for Ions and Gases

• Qualitative Identification Tests:

  • Hydrogen ($H_2$): Produces a squeaky pop with a lit splint.

  • Oxygen ($O_2$): Relights a glowing splint.

  • Carbon Dioxide ($CO_2$): Turns limewater milky.

  • Ammonia ($NH_3$): Emits a pungent smell and turns damp red litmus paper blue.

  • Chlorine ($Cl_2$): Bleaches damp litmus paper white.