Topic 4 – Extracting Metals & Equilibria Flashcards
Explain the advantages of recycling aluminium & iron rather than extracting them from their ores (6)
• less power / energy used
—> therefore conserves fossil fuels
• reduces waste in landfill sites
—> so less damage to habitats/landscape
• carbon dioxide is a greenhouse gas
—> greenhouse gases cause global warming
• avoids use of large amounts of electricity to extract aluminium from its ore
—> electricity is expensive
Explain why the reaction between metal Y and excess dilute sulfuric acid stopped even though there was solid metal Y left
• metal sulfate insoluble
• prevents further reaction of metal with acid
State an advantage of extracting nickel by phytoextraction rather than from its ore
• decontaminates ground / conserves nickel (ores)
• less noise due to mining / less carbon dioxide
Describe the experiments that can be done to determine the order of reactivity of these metals (Cu,Mg & Zn) by displacement reactions (3)
• place separate pieces of each metal into solutions of their salt (copper/magnesium/zinc sulfate)
• observe colour change in metal/solution
• the more reactive metal shows the greater number of reactions
Devise a simple method to obtain a sample of copper from copper oxide in the laboratory (2)
• react copper oxide with dilute hydrochloric acid
• electrolyse solution formed
Explain why aluminum cannot be extracted from its ore by heating with carbon but can be extracted by electrolysis (2)
• aluminum is more reactive than carbon (so electrolysis required)
• carbon cannot displace aluminum
• electrolysis can be used to reduce aluminum ions
Explain why electrolysis is used to extract aluminum from its ore
• aluminium is high in the reactivity series / very reactive / more reactive than carbon
• so it requires a lot of energy (to remove oxygen from oxide)
Explain why aluminum has to be extracted from its oxide by electrolysis and not by heating its oxide with carbon
• aluminum is high in reactivity
• aluminum (oxide) cannot be reduced by carbon
Disadvantages of phytoextraction to extract metals from low-grade ores
• slow process
• large area of land required
• only extracts metal from the ground surface
• metals need further extraction
• harmful/toxic gas released on burning plants
Advantages of recycling metals rather than extracting metals from their ores
• reduces waste
• reduces energy needed for metal extraction
• preserves habitats/landscape/resources
Metals found in the Earth’s crust as uncombined elements are…
Very unreactive (gold)
What type of metals are found in ores?
Reactive metals
(metals are combined with other elements in ores)
Stages of life-cycle assessment
• obtaining and processing the raw materials
• manufacturing the product
• using the product
• disposal of the product
Advantages of obtaining aluminum by recycling aluminium waste rather than mining the raw material & extracting aluminium from that raw material
• less damage to landscape/habitats
• less pollution/noise
• less energy required
• less waste metal goes into landfill
Describe how growing plants can result in phytoextraction of copper
• plants absorb copper/metal ions from soil/ores
• plants are harvested & burned (to leave copper/metal compound)
Ca & K react with water in similar ways. One similarity is that hydrogen gas is produced. State one other similarity in the products of the reactions of Ca & K with water
both form a hydroxide
State why potassium is higher in the reactivity series & reacts more vigorously with water than calcium
Potassium loses outer electrons:forms cations more easily
State why iron can be extracted by heating iron oxide with carbon
Iron is less reactive than carbon
State why electrolysis is not used to extract iron
• electrolysis is expensive
• heating with carbon is cheaper
• electrolysis requires a large amount of electricity
Advantage of producing a metal by electrolysis
Metal produced is very pure
The Haber process is an example of…
A reversible reaction
Describe how nitrogen is obtained
From the air (78%)
Describe how hydrogen is obtained
Extracted from hydrocarbons from natural gas & crude oil
3 conditions for Haber process:
• temperature: 450 degrees Celsius
• pressure: 200 atmospheres
• iron catalyst
Explain what is meant by dynamic equilibrium
• forward & backward reactions occur at the same time & at the same rate
• concentrations of reactants + produces are the same, won’t change
Explain why equilibrium can only be reached if the reversible reaction takes place in a closed system
• reactants + produces can’t escape
•
Le Chatelier’s Principle
if there’s a change in concentration, pressure or temperature in a reversible reaction, the equilibrium position will move to help counteract that change
Le Chatelier’s Principle – Temperature
• decreasing temperature
—> equilibrium moves in exothermic direction, to produce more heat
• increasing temperature
—> equilibrium moves in endothermic direction to absorb extra heat.
Le Chatelier’s Principle – Pressure
only affects equilibria involving gases
• increase in pressure
—> equilibrium moves towards the side with fewer moles of gas to reduce pressure
• decrease in pressure
—> equilibrium moves towards the side with more moles of gas to increase pressure
Le Chatelier’s Principle – Concentration
• increasing concentration of reactants
—> equilibrium moves to the right to use up reactants (making more products)
• increasing concentration of products
—> equilibrium moves to the left to use up products (making more reactants)
• decreasing concentration has opposite effect
