1i) Electrolysis

An electric current is the flow of electrons or ions. Covalent compounds can not conduct electricity because they make bonds by sharing electrons which means that they don't have any charge carriers that are free to move.

Electrolytes are liquids that conduct electricity:

Telling the difference between electrolytes and non-electrolytes:

When you place a conductivity probe in an electrolyte, the current flows through the circuit so you can measure its conductivity. When you place a conductivity probe in a non-electrolyte, no currents flow so the reading would be zero conductivity.

Another way of determining would be setting up an electrolytic cell, if the substance will undergo electrolysis then it is an electrolyte.

Electrolysis is when an electric current is passed through an ionic substance that's molten or in solution and it breaks down into a new substance(s). It is free electrons which conduct the electricity.

Example of Electrolysis is Molten Lead (II)Bromide or PbBr₂

Ion present: Pb²⁺ and Br^-

Ion attraction to electrode:

Cathode (-) Pb²⁺

Anode (+) Br^-

Half Equations of the electrodes show what is happening at each stage:

Cathode: Pb²⁺ + 2e^- → Pb

Anode: 2Br- → Br₂ + 2e^-

Electrolysis of aqueous solutions:

As well as the ions from the ionic compound there will be hydrogen ion (H+) and hydroxide ion (OH-) from the water

At the Cathode H+ ions or metal ions (if the metal is less reactive than hydrogen) are present

At the Anode OH- ions or a halide ion when they are in the experiment are present.

Examples:

Sulfuric Acid-

Contains three ions: SO₄^2-, H+ and OH-

Cathode (-) Hydrogen gas is produced:

half equation is 2H+ + 2e^- → H₂

Anode (+) Oxygen and water is produced:

half equation is 4OH- → 2H2O + 4e-

Copper (II) Sulfate-

Contains three ions: Cu²⁺, SO₄^2-, H+ and OH-

Cathode (-) Copper metal is produced:

half equation is Cu²⁺ +2e^- → Cu

Anode (+) Oxygen and water is produced:

half equation is 4OH^- → 2H₂O + 4e^-

Coulombs and Faradays are amounts of electricity:

• one amp flowing for a second means a charge of one coloumb has moved
• Q (charge) = I (Current) x t (Time)
• 96000 coulombs is called one faraday
• One faraday (F) contains one mole of electrons

1h) Metallic Crystals

Metals

• Have a giant structure of positive ions surrounded by free electrons
• Are held together by metallic bonding. They have a giant structure of positive ions surrounded by a sea of de-localised (free) electrons
• The attraction between the positive ions and electrons is called 'metallic bonding'
  It is the metallic bonding which gives metals their properties

Properties 

• hammered/ bent into shape 
• good conductors of heat and electricity due to the free electrons which carry the electrical  
• strong 
• malleable- atoms in a regular pattern in layers slide over eachother and can be hammered into shape

1e) Chemical Formulae and Chemical Equations

Word equations and Balanced chemical equations are used to represent the reactions studied in this specification. In a chemical equation you have to use state symbols: (s), (l), (g) and (aq) in chemical equations to represent solids, liquids, gases and aqueous solutions

Water of Crystallisation:

• solid salt with water is HYDRATED
• salt without water is ANHYDROUS
• calculate it by:

1. Working out the mass
2. Number of moles of water lost
3. ratio of anhydrous salt made
4. ratio of anhydrous to mole of Water
5. X must be a whole number

Empirical formula:

Is the simplest formula that tells you the ratio of different elements in the compound

1. List all the elements in the compound
2. Write underneath the experimental masses/ percentage
3. Divide by A_r of elements
4. Change to simple ratio by multiplying and/or dividing them by well chosen numbers
5. Simplify ratio

Molecular Formula:

A compound tells you the actual number of atoms each element in a single molecule

Calculate Masses in Reactions:

1. Write out the balanced equation
2. Work out the and multiply them by balancing numbers in the equation
3. Apply the rule: Divide to get one, then multiply to get all

Percentage Yield:

= (mass obtained/ mass predicted) x 100

Moles and Concentration

Concentration = Number of Moles / Volume

1d) Relative formula masses and molar of gases

Relative formula mass can be found by adding up the mass numbers

A mole is a precise number. When you get precisely that number of atoms or molecules, of any element or compound, they weight exactly the same number of grams as the relative atomic mass, A_r of the element or compound. One mole of atoms or molecules of any substance will have a mass in grams equal to the relative formula mass for that substance.

Example- Carbon has an A_r of 12 and so the one mole of carbon weighs exactly 12g.

The number 6.023x10²³ is called Avogadro's number or the Avogardo constant. So you can think of a mole as the Avogardo number of particles in a substance, where the articles are atoms, molecules, ions or electrons.

Number of moles = Mass in g/ M_r

One mole of any gas always occupies 24dmº (=24000 cmº) at room temperature and pressure (RTP: 25ºc and 1 atmosphere)

Volume (dm³) = moles of gas x 24

Volume (dm³) = (mass of gas/ M_r of gas) x 24

Changes

I've released that Section 1 of this specification is incomplete, so I'll be going back changing and adding new information.

End of Notes

The whole specification for IGCSE Chemistry has been completed. (Yay!)
Good Luck and happy studying.

5d) Industrial manufacture of chemicals

Nitrogen from the air and hydrogen from either natural gas or from the cracking of hydrocarbons are used in the manufacture of ammonia

Haber Process:
Manufacture of ammonia

Uses of ammonia
- fertiliser
- nitric acid
- nylon fabric

Paper Two - Sulfuric acid 

Raw materials used to manufacture it: sulfur and oxygen 

Contact Process 
Manufacture of sulfuric acid 
Stage one: sulfur and oxygen --> sulfur dioxide 
Stage two: sulfur dioxide and oxygen  sulfur trioxide 
Stage three: sulfur trioxide and conc sulfuric acid --> fuming sulfuric acid 
Stage four: fuming sulfuric acid and water --> sulfuric acid 

Conditions: 450C, 2 atmospheres of pressure and vanadiumn oxide (V2O5) catalyst 

Uses of sulfuric acid:
- fertilisers 
- detergents 
- paints and pigments 
- plastics 
- paper and fibres 

Electrolysis of Brine

Ions present: Na+ Cl- H+ OH- 
Ion attraction to electrode:
Anode (+)  Cl-     OH-
Cathode (-) Na+   H+

Actual products: at cathode is hydrogen due to the reactivity series; lower reacting one forms out of possible products 
at anode chlorine because if you have a halideion (group 7 ion) then the halogen will from, if not the oxygen will 

Half Equations:
Cathode - 2H⁺ + 2e^- --> H₂ 
Anode - 2Cl^- --> Cl₂ + 2e^-

Useful products

1. Chlorine: sterilise water supplies and also used to make bleach and HCl
2. Hydrogen: used in the haber process and changes oil into fat to make margarine 
3. Sodium Hydroxide: used to make soap, bleach and paper pulp