Chemistry 2b - created from Mind Map

Page 1

Rates of Reaction

Reaction rate=amount of reactant used up /time

What effects it?

Reaction types

Yield

Could measure (at timed intervals)...

Volume of gas formed

Number of bubbles formed

Time of for one reactant to dissolve

Temperature

Concentration

surface area

Catalysts

Increases energy and therefore kinetic energy

Increases frequency of collisions as there are more particles in the same volume

Collisions occur on surfaces

Include transition metals and their compounds

Reduce costs in industrial reactions

Different in different reactions

Molecules absorbed on catalyst surface

Exothermic

endothermic

Reversible= Exothermic one way, endothermic the other

energy to surroundings

energy from surroundings

Equilibrium occurs when reactions occur at same rate/both directions

Depends on conditions e.g. temperature

The amount of product obtained in a reaction

Better if:

Exothermic

High pressure

removing products and replenishing reactants

Electrolysis

Free ions

Equations

Uses

metals= positive

Non-metals= negative

When molten, free to move

move to neg. electrode

Cathode

move to pos. electrode

Anode

1/2 equations

Represent oxidations and reductions

e.g. Sodium chlordie

Na+ (aq) + e- --> Na (s)

2Cl-(aq)-->Cl2 (g) + 2e-

Reuction, pos/neg charge cancel out

Na+ gains 1 electron, has no charge

Oxidation, neg/pos charge balanced

2cl- loses 2 electrons

If the metal in the reaction...

Sulfate solutions give oxygen at anode

Is less reactive than hydrogen

Is more reactive than hydrogen

Metal comes out at cathode

Hydrogen stays in solution

any metal more reactive than hydrogen can react with an acid

We get hydrogen!

Metal stays in solution

Salts, Acids and Alkalis

Bases

Ammonia forms alkaline solution in water

All acids contain hydrogen ions

All Alkalis contain Hydroxide ions

In neutralisation reactions...

Precipitates

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

Would be good fertiliser, except to alkaline

React with acid and get neutral salt- perfect

H+

OH-

Hydrogen and hydroxide ions react to make water

They always produce a salt

Insoluble salts- can be made as precipitates

Ion impurities- removed from water supply if made into insoluble salts

Chemistry 2b