Dan Crowie IGCSE Chem0620 by Lizelle Swanepoel

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Kinetic theory of matter

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BONDING: METALLIC, IONIC, COVALENT

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METALS, NON-METALS, AND BONDING

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GIANT STRUCTURES

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ATOMS VS IONS

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Diffusion

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Diffusion is the spontaneous moving and mixing of substances into each other from a region of high to a region of low concentration.

Separating techniques

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Separating techniques

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Separating techniques

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Separating techniques

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Stoich

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Electrolysis

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NOTES 2022

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GIANT MOLECULES - MACROMOLECULES

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TESTS FOR GASES AND FLAME TESTS

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THE MOLE - SYLLABUS

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ELECTRICITY AND CHEMISTRY

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ENERGETICS IN CHEM

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CHEM REACTIONS

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ORGANIC CHEM

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QUALITATIVE TESTS

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AIR & WATER

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Electroplating animation

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Electrolysis of brine - general reaction

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ELECTROLYSIS OF NaCl solution

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EXAM QUESTION

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Reduction Potential Table Voltage Values

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The Voltage value shows how easily the element is reduced.

A negative Voltage reduction potential value means:

negative value = DIFFICULT to be reduced.
the other element or compound has a greater tendency to REDUCED.

A positive value means:

positive value = EASY to be reduced.
The other element or compound has a greater tendency to be OXIDISED.

2. ELECTROLYTIC CELL: E electrical —> E chemical. Using electricity to make a chemical reaction occur

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ELECTROLYSIS
ELECTROLYTIC CELLS

USES OF ELECTROLYTIC CELLS - ELECTROPLATING

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Electroplating = a method of using an electric current to deposit a thin layer of metal over another from a solution containing a dissolved salt of the selected metal.

NOTE:
The anode is connected to the positive terminal:

The anode is generally composed of the material that we want to deposit.
E.g. Copper in the case of copper plating, nickel in the case of nickel plating.
It is also possible to plate using “inert” anodes like carbon rods in certain cases.

The cathode connected to the negative terminal:

The cathode is the component on which we intend to deposit the metal.
In a plating workshop this is commonly referred to as the “work-piece”.

The English physicist Michael Faraday (1791 – 1867) provided us with the important rules that govern electro-deposition:

He showed that the amount of metal deposited at the cathode and the amount dissolved at the anode are directly proportional to the quantity of electricity passed, in other words, to the current and time period of the electro-deposition.
Thanks to Faraday's efforts and Faraday's Constant (F = 96 500 C), we can calculate the deposit mass of any metal that we are plating based on its atomic mass and the number of electrons involved in the electrochemical reaction. The formula use is:
n = q/F (where n=number of moles of e^- transferred between electrodes, q=charge, F=96500 C)

Cu vs Nitrate ions on redox table

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NO₃^-ions would be reduced in preference over Cu²⁺ions in the electrolyte solution.

So, to electroplate a medal with Copper, do not use copper(II) nitrate as electrolyte.
Use CuSO₄(aq)

Copper purification

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Electroplating questions

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Chlor-alkali industry

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Exercise

Membrane cell (Chlor-alkali industry)

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Extraction of aluminium

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ELECTRICITY AND CHEMISTRY

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MOLTEN LEAD(II) BROMIDE ELECTORLYSIS

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HCl electrolysis

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Exam questions

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Exam questions

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Exam questions

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Exam questions

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Memos

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Memos

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Memos

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CHEMICAL EQUILIBRIUM

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CHEMICAL EQUILIBRIUM

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INTRODUCTION

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Two key points:

A reversible reaction = a reaction that can proceed in both the forward and backward directions, whereby products can re-form reactants in a CLOSED SYSTEM.

Equilibrium = a reaction state where the rate of the forward reaction equals the rate of the reverse reaction. All reactant and product concentrations are constant at equilibrium.
DYNAMIC EQUILIBRIUM = A reaction in which the rate of the fwd reaction equals the rate of the reverse reaction in a closed system, where the fwd and rev reactions occur simultaneously.

Le Chatelier's Principle

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DEFINITION:
When an external stress (change in pressure, temperature or concentration) is applied to a system in chemical equilibrium, the equilibrium point will change in such a way as to counteract the stress.

FACTORS AFFECTING CHEMICAL EQUILIBRIUM

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STRESSES (DISTURBANCES) CAN BE:

CONCENTRATION (OF REACTANTS OR PRODUCTS)
PRESSURE (ONLY IF REACTION SPECIES ARE GASES)
TEMPERATURE

FACTORS AFFECTING CHEMICAL EQUILIBRIUM

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STRESSES (DISTURBANCES) CAN BE:

CONCENTRATION (OF REACTANTS OR PRODUCTS)
PRESSURE (ONLY IF REACTION SPECIES ARE GASES)
TEMPERATURE

FACTORS AFFECTING CHEMICAL EQUILIBRIUM

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STRESSES (DISTURBANCES) CAN BE:

CONCENTRATION (OF REACTANTS OR PRODUCTS)
PRESSURE (ONLY IF REACTION SPECIES ARE GASES)
TEMPERATURE

HOW TEMPERATURE CHANGE STRESS AFFECT CHEM EQUILIBRIUM

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REMEMBER:
FOR EXOTHERMIC RXN (ΔH<0 or negative value for ΔH given):

If the stress is that T decreases, then response is FWD RXN FAVOURED.
If the stress is that T increases, then response is that REV RXN IS FAVOURED.

FOR ENDOTHERMIC RXN (ΔH>0 or positive value for ΔH given):

If stress is: T increases, then response is that FWD RXN IS FAVOURED.
If stress is: T decreases, then response is that REVERSE RXN IS FAVOURED.

Key: RXN = reaction, FWD = forward, REV = reverse

EXERCISE 1

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AIR & WATER

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SULPHUR IS S8

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SULPHUR POWDER

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CONTACT PROCESS - H2SO4 FROM SO2

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Fertilisers

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N, P, K Fertilisers
Fertilisers contain nitrogen, potassium and phosphorus
Nitrogen makes chlorophyll and protein and promotes healthy leaves
Potassium promotes growth and healthy fruit and flowers
Phosphorus promotes healthy roots
Fertiliser compounds contain the following water-soluble ions:
Ammonium ions, NH4+ and nitrate ions, NO3-, are sources of soluble nitrogen
Phosphate ions, PO43- are a source of soluble phosphorus
Most common potassium compounds dissolve in water to produce potassium ions, K+
Common fertiliser compounds include:
Ammonium nitrate, NH4NO3

Ammonium phosphate, (NH4)3PO4

Potassium sulfate, K2SO4
Ammonium salts and nitrates are commonly used as fertilisers
Different fertilisers contain different amounts of fertiliser compounds so each contains different proportions of nitrogen, potassium and phosphorous

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PAPER 6- Practical part

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