Chemistry unit 2

Topic 2.1: Bonding, Structure & Properties

Define Ionic Bonding;The electrostatic attraction between oppositely charged ions.

Why do giant ionic lattices have high melting points?;Strong electrostatic forces between ions in all directions require a lot of energy to break.

When do ionic compounds conduct electricity?;Only when molten or in solution, as the ions are free to move and carry charge.

Define Covalent Bonding;A shared pair of electrons between two non-metal atoms.

Why do simple molecular substances have low boiling points?;They have weak intermolecular forces which require little energy to break.

Why does Diamond have a very high melting point?;Each carbon is covalently bonded to 4 others in a giant rigid lattice; these bonds are very strong.

Why can Graphite conduct electricity?;Each carbon has 3 bonds and 1 delocalised electron that is free to move between layers.

Why is Graphite soft and slippery?;Weak forces between layers allow the layers to slide over each other.

Describe Metallic Bonding;A giant lattice of positive metal ions surrounded by a sea of delocalised electrons.

Why are metals malleable?;The layers of ions can slide over each other without breaking the metallic bonds.

What is a Nanoparticle?;A particle between 1–100nm in size with a very high surface area to volume ratio.

What is a Smart Material?;A material that changes its properties in response to an external stimulus (temp, light, etc.).

What does a Thermochromic pigment do?;Changes colour when the temperature changes.

What does a Shape Memory Alloy do?;Returns to its original shape when heated.

Topic 2.2: Acids, Bases and Salts

Acid + Metal → ?;Salt + Hydrogen

Acid + Metal Oxide → ?;Salt + Water

Acid + Metal Carbonate → ?;Salt + Water + Carbon Dioxide

Define a Strong Acid;An acid that fully ionises/dissociates in water to release H+ ions.

Define an Alkali;A soluble base that releases OH- (hydroxide) ions in water.

What is the test for Hydrogen gas?;A lit splint makes a 'squeaky pop'.

What is the test for Carbon Dioxide?;Bubble through limewater; it turns cloudy/milky.

Colour of Methyl Orange in acid vs alkali;Red in acid, Yellow in alkali.

Colour of Phenolphthalein in acid vs alkali;Colourless in acid, Pink in alkali.

How do you make a soluble salt from an insoluble base?;Add excess base to acid, filter the excess, evaporate water from filtrate, and crystallise.

Define a neutralisation reaction;A reaction between H+ ions and OH- ions to form water (H2O).

Topic 2.3: Metals and Their Extraction

Define an Ore;A rock containing enough metal compound to be worth extracting.

Define Reduction (in terms of oxygen);The loss of oxygen.

Define Oxidation (in terms of oxygen);The gain of oxygen.

How are metals less reactive than carbon extracted?;Reduction by heating with Carbon.

How are metals more reactive than carbon extracted?;Electrolysis.

Role of Cryolite in Aluminium extraction;Lowers the melting point of the electrolyte to save energy.

Why must Carbon anodes be replaced regularly?;They react with oxygen to form CO2 and wear away.

At which electrode is the metal formed?;The Cathode (negative electrode).

Benefits of recycling metals;Saves raw materials, uses less energy than extraction, reduces landfill.

Topic 2.4: Chemical Reactions and Energy

Define Exothermic;A reaction that gives out heat energy to the surroundings (Temp increases).

Define Endothermic;A reaction that takes in heat energy from the surroundings (Temp decreases).

Define Activation Energy;The minimum energy required for a successful collision.

Bond breaking is...;Endothermic (requires energy).

Bond making is...;Exothermic (releases energy).

Formula for Energy Change;Energy of bonds broken - Energy of bonds made.

Topic 2.5: Crude Oil and Organic Chemistry

Define a Hydrocarbon;A compound containing hydrogen and carbon ONLY.

How is Crude Oil separated?;Fractional distillation based on boiling points.

General formula for Alkanes;CnH2n+2

General formula for Alkenes;CnH2n

General formula for Alcohols;CnH2n+1OH

Difference between Saturated and Unsaturated;Saturated has only single C-C bonds; Unsaturated has at least one C=C double bond.

Test for Alkenes;Add Bromine water; it turns from orange to colourless.

Define Isomers;Molecules with the same molecular formula but different structural formula.

What is Addition Polymerisation?;Many small monomers (alkenes) join to form a long chain polymer.

Pros of Fermentation for Ethanol;Uses renewable resources, low energy/cost.

Pros of Hydration of Ethene for Ethanol;Fast reaction, produces very pure ethanol.

Topic 2.6: Reversible Reactions & Industrial Processes

Define Dynamic Equilibrium;Forward and reverse reactions occur at the same rate in a closed system.

Conditions for the Haber Process;450°C, 200 atm pressure, Iron catalyst.

Equation for the Haber Process;N2 + 3H2 ⇌ 2NH3

Haber Process: Effect of increasing pressure;Shifts equilibrium to the right (side with fewer moles) to increase yield.

Haber Process: Effect of increasing temperature;Shifts equilibrium to the left (endothermic direction) to decrease yield.

Contact Process catalyst;Vanadium(V) Oxide (V2O5).

What is Sulfuric Acid used for?;Making fertilisers, detergents, and paints.

Topic 2.7: Practicals & Math (Ion Tests)

Flame test: Lithium;Red

Flame test: Sodium;Yellow-Orange

Flame test: Potassium;Lilac

Flame test: Calcium;Brick-Red

Flame test: Barium;Apple-Green

How to test for Halide ions (Cl-, Br-, I-);Add Silver Nitrate solution.

Silver Nitrate results;Chloride = White ppt, Bromide = Cream ppt, Iodide = Yellow ppt.

Formula for Moles;Mass / Relative Atomic Mass (Ar or Mr).

Formula for % Yield;(Actual Yield / Theoretical Yield) x 100.

Formula for Atom Economy;(Mass of desired product / Total mass of reactants) x 100.