Equilibria ⇌

Reversible Reactions In Reversible Reactions the products can react to form the original reactants Equilibrium reactions refer to the forward reaction (left to right) and the backwards reaction A reversible arrow is used ⇌

Reaction conditions An equilibrium only occurs if the reaction is in a closed system where nothing can get in or out. In a dynamic equilibrium the forward reaction and the backwards reaction occur at the same time and rate.

Industry Changing the reaction conditions, changes the equilibrium position and therefore the amount of reactants or products. This is important in industry where many products are made in equilibrium reactions.

The Haber Process Ammonia is made by the Haber Process Nitrogen + Hydrogen ⇌ Ammonia N2 + 3 H2 ⇌ 2 NH3 Nitrogen is from the fractional distillation of air and Hydrogen is obtained from methane.

Conditions for the Haber Process A high temperature increases the rate of reaction, but reduces the yield of Ammonia because the forward reaction to make ammonia is exothermic. A high pressure increases the rate of reaction, but is too expensive. Increasing the pressure favours the side of the equilibrium with the least number of gaseous molecules. Compromise temperature 450 oC and 200 atm pressure are used.

Economics of the Haber Process Using an Iron catalyst does not affect the position of the equilibrium, but it increases the rate of reaction and reduces the cost of the process. Iron is a cheap catalyst. Ammonia is cooled, liquefied and removed as soon as it is made to stop it decomposing. Unreacted Nitrogen and hydrogen are recycled. Ammonia is used to make fertilisers.

Organic Chemistry C2H5OH

Hydrocarbons Organic molecules contain carbon compounds Alkanes and Alkenes are hydrocarbons Ethane, C2H6 Ethene, C2H4

- OH - COOH - COOR Functional Groups A functional group is the part of the molecule that is involved in chemical reactions. Replacing an H atom with a functional group makes other organic compounds: Alcohols, Carboxylic acids, Esters - OH - COOH - COOR

Alcohols Alcohols are a homologous series of compounds containing the – OH group. Ethanol, with a structural formula of C2H5OH. Displayed formula Ethanol is the alcohol found in drinks.

Properties of Alcohols They are Flammable and used as fuels Combustion of Ethanol : C2H5OH + 3O2 → 2CO2 + 3H2O They react with Sodium to produce Hydrogen, but this is slower than sodium with water.

Oxidation of Alcohols They can be oxidised to Carboxylic acids by boiling with potassium dichromate E.g. Ethanol makes Ethanoic acid (Vinegar)

Carboxylic Acids These are weak acids with pH values higher than for strong acids. Strong acids are fully ionised, but weak acids are partially ionised. CH3COOH ⇌ CH3COO- + H+ Weak acids have a lower concentration of Hydrogen ions, H+.

Esters Concentrated Sulphuric acid is the catalyst. Carboxylic acids and Alcohols react to make Esters. Carboxylic acid + Alcohol → Ester + Water Ethanoic acid + Ethanol → Ethyl ethanoate + Water CH3COOH + CH3CH2OH →CH3COOCH2CH3 + H2O Concentrated Sulphuric acid is the catalyst.

Properties of Esters Ethanoic acid + Methanol ⇌ Methyl ethanoate + Water Esters are volatile – evaporate easily. They are sweet smelling and fruity. Uses include as perfumes and food additives