extracting metals & equalibria Flashcards
What does calcium + water make?
Calcium hydroxide + hydrogen
What does a metal + acid make?
Salt + hydrogen
What is a displacement reaction?
The more reactive metal displaces the less reactive metal
What do more reactive metals become?
Cations by losing electrons in oxidation.
How do you extract higher placed metals? Why?
Electrolysis, too reactive
How do you extract lower placed metals?
Heating with carbon
What is the reactivity series?
PSCMACZITLHCSG
What is phytomining?
Plants absorb metals through roots, parts of plant are harvested, dried & burned. Resulting ash contains metal compounds to be extracted.
What is bioleaching?
Some strains of bacteria can break down ores to form acidic solutions (leachate) containing metal ions. Ions can be reduced to solid metal form & extracted.
What are the 4 stages of a LCA?
Raw materials
Manufacture
Usage
Disposal
Why is obtaining raw materials negative?
- Using up limited resources (ores & crude oil)
- Damaging habitats (deforestation or mining)
Why are manufacturing processes negative?
- Using up land for factories
- Use of fossil fuelled machines
Why is disposal negative?
- Using up space at landfill sites
- Whether product or parts can be recycled
What are reversible reactions?
The reaction occurs in the forward reaction (forms the products) & the backward reaction (forms the reactants)
A + B ⇌ C + D
What is equilibrium?
When rate of forward reaction equals rate of backward reaction, the overall reaction is said to be in a state of equilibrium.
(Equilibrium is dynamic)
The concentration of reactants & products remains constant, & only occurs in a closed system.
What are the conditions for the Haber process?
Temperature: 450ºC
Higher temp favours reverse reaction having higher yield of reactants. Lower temp - rate of reaction is very slow
Pressure: 200 atm
Lower pressure favours reverse reaction having higher yield of reactants
Higher pressure favours forward reaction having higher yield of products
Catalyst
A catalyst of iron is used to speed up the reaction
What is the Haber process?
- H₂ and N₂ obtained from natural gas & are pumped into compressor through pipe
- Gases compressed to about 200 atmospheres
- Pressurised gases pumped into tank with layers of catalytic iron beds at 450°C. Some hydrogen and nitrogen react to form ammonia:
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g) - unreacted H₂ and N₂ & product ammonia pass into cooling tank.
- Ammonia is liquefied & removed to pressurise storage vessels
5: Unreacted H₂ and N₂ gases are recycled back into system & start again
