Section 13

Question 1

The reactivity series

Answer 1

OIL RIG
Combustion reactions involve oxidation- these are always exothermic
Metals at bottom don’t give up electrons easily
Metals at top easily lose electrons to form cations (+)

Question 2

Reactivity of metals

Answer 2

Some metals also react with water = metal + water =metal hydroxide + hydrogen
How metals react with acids tells you about their reactivity- the more easily atom loses outer electrons to be positive, more reactive
Test - place little pieces of metals into dilute HCL- louder the squeaky pop, more hydrogen, more reactive = faster the reaction

Question 3

Displacement reactions

Answer 3

More reactive metals displace less reactive ones
Displacement reactions are redox reactions , meaning oxidation and reduction happen simultaneously
OIL RIG
More reactive metal is oxidised - less reactive metal is reduced

Question 4

Extracting metals using carbon

Answer 4

Ores contain enough metal to make extraction worthwhile 
Above carbon = electrolysis 
Below carbon (silver but not gold) = reduction with carbon 
Silver and gold = uncombined elements

Question 5

Other methords of extracting metals

Answer 5

Phytoextraction - involves growing plants in soil that contains metal compounds
Bioleaching- uses bacteria to separate metals from their ore - biological methord
Electrolysis- metal is discharged at cathode, non metal at anode - more expensive than reduction with carbon

Question 6

Recycling

Answer 6

Conserves resources and energy- metals are non renewable
Protects the environment- cuts down amount going into landfill-takes up space and pollution
Has economic benefits- more jobs, beneficial to economy to recycle expensive metals

Question 7

Life-cycle assessments

Answer 7

LCA looks at each stage of life of a product – it works out the potential environmental impacts at each stage

1. choice of material – have to be mind, need energy= Pollution pollution
2. manufacture – uses energy
3. products used – using product damages environment
4. disposal – often disposed in landfill which pollutes

Question 8

Dynamic equilibrium

Answer 8

Dynamic equilibrium – forward and backward reactions both at same rate and concentration
Three things that change position of equilibrium – temp, pressure, concentration

Question 9

Reversible reactions

Answer 9

Reversible reactions - Products forming from reactants and reactants forming from products
A+ B C plus D
Reversible reactions will reach equilibrium – as A and B react the concentration fall so forward reaction will slow down – but as more products (C and D) are made concentrations rise backward reaction speeds up – after a while, forward and backward reaction will be going at the same rate = equilibrium

Question 10

Le chateliers principle - temperature

Answer 10

Temperature – or reactions are exothermic in One Direction and endothermic in the other – if you decrease temp equilibrium will move in exo Direction to produce more heat, if increase, equilibrium moves in endo Direction to absorb heat

Question 11

Le chateliers principle - concentration

Answer 11

If increase reactants, equilibrium moves to right to use up reactants - if increase products, equilibrium moves to left to use products– If decrease, it has opposite affect

Question 12

Le chateliers principle

Answer 12

States that if there is a change in temp, concentration or pressure in a reversible reaction, the equilibrium position will move to help counteract that change

Question 13

Le chateliers principle - pressure

Answer 13

Increase, equilibrium will move towards side with fewer moles of gas to reduce pressure – if decrease, equilibrium will move towards side with more moles of gas to increase pressure