Topic 6 Flashcards
Copper is a valuable
Metal
We are running out of high-grade
Copper ores
It is expensice to extract copper from
Low-grade ores using traditional methods
Scrap iron can be used to produce copper from solutions of copper salts :
Iron + copper sulfate -> iron (II) sulfate + copper
Fe(s) + CuSO4(aq) -> FeSO4 (aq) + Cu(s)
As the grade of ores go from High to low the proportion of metal or metal compound goes from
High to low
Compared with High-grade ores, low-grade ores:
Are more common because most High grade ores have already been used
Are less profitable
Use more energy
Produce more waste when used
What’s phytoextraction
A biological method of metal extraction that used plants
What happens in phytoextraction
Metal compounds absorbed by roots
Plant concentrates metal compounds in its shoots and leaves
Plants burned
Ash contains metal compounds
What’s bioleaching
A biological method of metal extraction that used bacteria.
Copper can be extracted from copper sulfate in the following way
The bacteria oxidise sulfide ions S2-
Copper sulfide ores break down
Cu2+ ions are released
The solution that bacteria produce is called a leachate.
What does a leachate contain
A high concentration of metal ions
Scrap iron can be used to obtain copper from the leachate
Disadvantages of extracting metals
Used up limited resources
Uses a lot of energy
Damages environment
Recycling reduces these disadvantages. Used metal items are collected. Rather than throwing them away. These are taken apart. The metal is melted down to make new items
Recycling metals advantages
Metal ores will last longer Less energy is needed Fewer quarries and mines are needed Less noise and dust are produced Less land is needed
Drawbacks of recycling
Used metal items must be collected and transported to the recycling centre
Different metals must be removed from used items and sorted
Recycling saves different amounts of energy, depending on the metal involved
Recycling metals save energy
Different amounts of energy are saved by recycling metals compared with extracting them from ores
Aluminium 94% energy saved
Copper 86% energy saved
Iron and steel 70% energy saved
what’s a LCA
Life cycle assessment
Cradle to grave
A life cycle assessment of a product is a ‘cradle to grave’ analysis of its impact on the environment
What stages are in a cradle to grave
Obtaining raw materials
Manufacturing the product
Using the product
Disposing of the product
An LCA is likely to need data on these factors at most or all stages:
The use of energy
The release of waste materials
Transport and storage
An LCA is also likely to need data on:
Whether the raw materials needed are renewable or non-renewable
Whether any of the product can be recycled or re used
How the product is disposed of
An example of a life cycle eg a car
Obtaining raw materials Processing raw materials Making car Using and making car End of useful life Disposal
Where are transition metals palaced
Between group 2 and 3
Typical properties of transition metals
High melting point (except mercury, which is in the liquid state at room temperature) High density (they have a high mass for thei volume)
Are transition metals stronger And harder than the metals in groups 1 and 2
Yes so they are often more suitable as construction materials
Chemical properties of transition metals
Formation of coloured compounds
Catalytic activity
Transition metals and their compounds are often useful as
Catalysts
Catalysts increases the rate of a chemcial reaction without :
Altering the products of the reaction
Changing chemically
Changing in mass at the end of the reaction
Group 1 and 2 typical properties include
Relatively low melting point
Relatively low density
Formation of white or colourless compounds
Lack of catalytic activity
These properties are the opposite of those for transition metals
The oxidation of metals results in
Corrosion
The corrosion of iron and steel is called
Rusting
Equation for rusting
Iron + oxygen + water -> hydrated iron (iii) oxide
Rust prevention may rely on keeping oxygen and water away from the surface of the iron or steel rays to do this include
Painting
Using oil or grease
Coating with plastic
Coating with another metal
Rust prevention may keep oxygen away
Store the item in a vacuum container
Rust prevention may keep water away
Put the item in a container with a desiccant
The method of rust prevention you choose depends on
Factors such as cost and sustainability
The inside of a food van is protected by a then layer of tin
You would not want to use oil or grease
A metal object can be electroplated to:
Improve its appearance
Improve its resistance to corrosion
Electroplating
A thing layer of an unreactive metal such as nickel, silver or gold is deposited on the surface of the metal object, keeping air and water out
What is an alloy
A mixture of a metal with one or more other elements
These other elements are usually other metals or carbon
Pure iron is too soft for most purpose. It is mixed with carbon and other metals to produce alloys called
Steels
There are many types of steel with different uses depending on their properties. The most common steels are
Carbon steels they:
Consist of iron with up to 2% carbon
Are harder and stronger than iron alone
What is stainless steel
Is an iron alloy that resists corrosion it is used to make cutlery washing machine drums and dishwashers
Stainless steel contains chromium :
An invisible thin layer of chromium oxide forms on the surface of the steel
It stops air and water reaching the iron
They layer quickly reforms if its scratched
Concentration =
Amount of solute / volume of solution
You can easily convert between mol dm -3 and g/dm 3 using the Mr of the solute :
Mol do-3 -> g dm -3 - multiply the concentration by the Mr
G dm-3 -> mol dm-3 - divide the concentration by the Mr
