Types of chemical reactions

Acid and Bases

pH and indicators

formation of salts

Redox reactions

Reactivity series

Electrochemical cells

Neutralisation is when a reaction occurs with acid that gives water as well as a salt

Used to reduce acidity in soil using slaked lime ( CaOH ) and calcium carbonate ( CaCO3), and neutralisation takes place

Equation for neutralisation : HCl + NaOH --> NaCl + H2O, with Cl being the non-metal and sodium being the metal to produce the salt.

Acid reactions

acid+metal --> salt+hydrogen

acid + base --> salt+water

acid + metal carbonate --> salt + water + carbon dioxide

Base reactions

Bases react with acids

Bases like sodium, potassium and calcium hydroxide react with ammonia salts to produce ammonia gas

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predicts chemical reactivity of an element

determines extent of a chemical reaction

weak acids that determine concentration of H+ via color change

Examples : Methyl orange, Methyl red, Phenolphthalein

Electrolysis

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Electrode

The electrodes are anodes and cathodes that are attached respectively each to the negative and positive terminal of a cell

the solution gets decomposed, and the ions carry current through liquid and electrons carry the current through wire.

At the cathode ( - ) , metal or hydrogen forms, and anode ( + ), a non-metal except hydrogen forms.

able to form salts by reacting acid with metals, insoluble bases, or soluble base, and carbonates

Extraction of metals

Iron

Aluminium

Zinc

Corrosion

Method : Add salt to dilute acid to dissolve it when warming, and solution changes color. Add until no more will dissolve. Remove solid by filter, and heat solution to form crystals.

Making insoluble salts through precipitation

Ex : Barium sulfate ( insoluble salt ) mix barium chloride and magnesium sulfate.

Process : Mix solutions, forms precipitate. Filter precipitate and rinse with distilled water. Place in warm oven to dry.

Uses of precipitation

Coloured pigments for paint

cleaning up waste water

Making photography film

Extracted through electrolysis

Iron is extracted through a blast furnace.

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Reactions in the blast furnace

Stage 1 : combustion, redox reaciton. Reaction is exothermic to heat the furnace

Stage 2 : Endothermic to take in heat from the furnace

Stage 3 : Redox Reaction ( Iron(III) oxide + carbon monoxide --> iron + carbon dioxide )

Charge containing iron ore, limestone and coke is added in the top of the furnace

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Alumina melts at high temperature, so it is dissolved in molten cryolite.

At the cathode, aluminium gains electrons and drops to the bottom as a molten metal

At the anode, oxygen loses electrons and reacts with anode to eat carbon. Needs to be replaced while alumina is broken down. ( 2Al2O3 --> 4Al + 3O2 )

For Zinc blende. Mainly zinc sulfide. It is obtained by roasting in the air giving zinc oxide and sulfur dioxide

Using carbon monoxide, where it is in a furnace ( ZnO + CO --> Zn + Co2 )

Reaction goes either direction. either forward or backward reaction

Endothermic or exothermic in the other. Same amount of energy transferred each time

Ex : Blue crystals are heated to turn into white powder. The reaction is easily reversible by adding water. the anhydrous copper(II) sulfate gets hot and turns back to blue

Corrosion of iron and steel is called rusting

Objects like a car gets corroded by being broken down by reaction with something in the atmosphere

Prevent rusting by ensuring oxygen and water do not react with the metal

When rusting occurs, iron becomes oxidised, since magnesium is more reactive, it loses electrons more easily. Magnesium dissolves to protect iron.

Oxidaition :lose electron, increase oxidation state, gain oxygen