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421812
Chemistry 2b
Descrição
Chemistry C2b based on the Collins Science Revision book for Additional Science at GCSE. Lacks some detail, especially on salts, acids and alkalis.
Sem etiquetas
chemistry
gcse
chemistry
gcse
Mapa Mental por
Alfie Ross
, atualizado more than 1 year ago
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Criado por
Alfie Ross
mais de 10 anos atrás
208
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Resumo de Recurso
Chemistry 2b
Rates of Reaction
Reaction rate=amount of reactant used up /time
Could measure (at timed intervals)...
Volume of gas formed
Number of bubbles formed
Time of for one reactant to dissolve
What effects it?
Temperature
Increases energy and therefore kinetic energy
Concentration
Increase collision freqeuncy
more particles for same volume
surface area
Collisions occur on surfaces
Catalysts
Include transition metals and their compounds
Different in different reactions
Reduce costs in industrial reactions
Molecules absorbed on catalyst surface
Reaction types
Exothermic
energy to surroundings
endothermic
energy from surroundings
Reversible= Exothermic one way, endothermic the other
Equilibrium occurs when reactions occur at same rate/both directions
Depends on conditions e.g. temperature
Yield
The amount of product obtained in a reaction
Better if:
Exothermic
High pressure
removing products and replenishing reactants
Electrolysis
Free ions
metals= positive
move to neg. electrode
Cathode
Non-metals= negative
move to pos. electrode
Anode
When molten, free to move
Equations
1/2 equations
Represent oxidations and reductions
e.g. Sodium chlordie
Na+ (aq) + e- --> Na (s)
Reuction, pos/neg charge cancel out
Na+ gains 1 electron, has no charge
2Cl-(aq)-->Cl2 (g) + 2e-
Oxidation, neg/pos charge balanced
2cl- loses 2 electrons
Uses
If the metal in the reaction...
Is less reactive than hydrogen
Metal comes out at cathode
Hydrogen stays in solution
any metal more reactive than hydrogen can react with an acid
Is more reactive than hydrogen
We get hydrogen!
Metal stays in solution
Sulfate solutions give oxygen at anode
Salts, Acids and Alkalis
Bases
metal oxides and hydroxides
React with acids
Make salts
acid+metal=metal salt+hydrogen
acid+ammonia= ammonium slat
acid+soluble/insoluble base=metal salt +water
Ammonia forms alkaline solution in water
Would be good fertiliser, except to alkaline
React with acid and get neutral salt- perfect
All acids contain hydrogen ions
H+
All Alkalis contain Hydroxide ions
OH-
In neutralisation reactions...
Hydrogen and hydroxide ions react to make water
They always produce a salt
Precipitates
Insoluble salts- can be made as precipitates
Iron impurities
make into insoluble salts to remove from water
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