Metals, Elimination, Substitution And Alkenes Flashcards
In oxides and sulfides the metals have positive oxidation states. When oxygen/sulfur is separated from the metal by…
Reduction
Which two elements are metals usually found combined with?
Sulfur and oxygen
What is gangue?
The unwanted materials such as clay and rock
Before reduction what are sulfide ores usually converted into and how?
They are converted into oxides by heating them in air, a process called roasting.
Give an example of a metal sulfide bing roasted
Zinc sulfide is converted into zinc oxide
ZnS (s)+ 1.5 O2 (g) —> ZnO (s) + SO2 (g)
How do you stop sulfur dioxide leaking into the environment and causing acid rain?
Sulfur dioxide can be converted into sulfuric acid. It can then be sold.
SO2 (g) + H2O (g) + 0.5 O2 (g) —> H2SO4 (l)
List some possible reducing agents for extracting metals.
Coke
Hydrogen
Sodium/aluminum (reduced by electrolysis)
More reactive metal (displaced)
Why is coke a good reducing agent when extracting metals?
It is cheaply obtained by heating coal in the absence of air. But for some metals the temperature required for reaction with carbon is so high that that the process is uneconomic. Also at high temperature reactive metals react with carbon to form carbides.
What are the main iron ores and what is the main impurity?
Magnetite (Fe3O4) and hematite (Fe2O3) a major impurity is silica SiO2
What is iron reduced by?
Coke
Where is iron reduced?
In a blast furnace
Describe iron extractions and the chemical equations included in it.
At the bottom of the furnace the coke burns in a blast of hot air. Heat is generated by this exoteric process so that the temperature is around 2000K. The carbon dioxide reacts with more carbon to form carbon monoxide.
C (s) + O2 (g) —> CO2 (g)
CO2 (g) + C (s) —> 2CO (g)
The carbon monoxide is the reducing agent. It reacts with the iron oxide to produce molten iron.
Fe2O3 (s) + 3CO2 (g) —> 2Fe (l) + 3CO2 (g)
Which other metal aside from iron is a reduction of its oxide with carbon?
Manganese and copper
What is the copper ore?
Malachite
Give the reaction for heating copper carbonate…
CuCO3 —-> CuO + CO2
What happens to the copper oxide?
It is heated with coke…
2CuO (s) + C (s) —> 2Cu (l) + CO2 (g)
What is an alternative way to extract copper now?
Reduction with scrap iron:
Cu2+ (aq) + Fe (s) —> Cu (s) + Fe2+ (aq)
Why is Reduction with scrap iron economically sensible?
The price of copper is much greater than iron and no carbon dioxide is produced in the extraction process and it uses much less energy than it takes in (but remember iron had to be extracted initially which takes energy).
What ore is aluminium extracted from?
Bauxite ore which is largely aluminium oxide
How is aluminium extracted?
Aluminium oxide is dissolved in molten cryolite Na3AlF6 to form a solution which melts at around 1240K, compared with the melting temperature of pure aluminium oxide 2345K. It is electrolysed in rows of cells.
In the electrolysis of aluminium oxide, what is produced at the negative electrode? What is the equation for it?
2Al3+ + 6e- —–> 2Al
In the electrolysis of aluminium oxide, what is produced at the positive electrode? What is the equation for it?
Oxygen
3O2- —-> 1.5 O2+6e-
What is the equation for the electrolysis of aluminium oxide?
Al2O3 —-> 2Al + 1.5 O2
Is the extraction of aluminum continuous?
Yes, the extraction of aluminium is continuous.
How is the solution of aluminium oxide kept molten in aluminium extraction?
By the heat generated by the flow of current
How is extracted aluminium formed?
As a liquid and it is siphoned off
The oxygen burns the carbon electrodes away to form….
Carbon dioxide (they must be replaced often)
What is the main cost of aluminium extraction?
The electricity used to do it.
What are useful properties of aluminium?
It is strong low density and resistant to corrosion
Why can’t titanium oxide be reduced with carbon?
Titanium carbide forms - brittle
How is titanium extracted?
By the reduction with a more reactive metal (sodium or magnesium)
Why is aluminium extraction so expensive?
It requires electrolysed magnesium/sodium and it involves two different processes.
What is the titanium ore?
Rutile (titanium 4 oxide)
How is rutile converted to titanium chloride?
Rutile is converted to titanium (4) chloride by reacting it with coke and chlorine at 1173K:
TiO2 (s) + 2C (s) + 2Cl2 (g) —-> TiCl4 (l) + 2CO (g)
How is titanium chloride purified?
By distillation
I what happens in the second stage of titanium extraction?
Titanium chloride is reduced with molten sodium (or sodium) under an inert argon atmosphere at 1300K. The argon is needed to prevent the metals from reacting with nitrogen and oxygen in the air.
TiCl4 (l) + 4Na (l) —-> Ti (l) + 4NaCl (l)
What kind of process is titanium extraction?
Batch process - less efficient - the reaction vessels have to be heated back up to operating temperature after the batch is removed.
Tungsten is very
Rare
Tungsten cannot be reduced by carbon because…
A carbide is formed
What is the equation for the extraction of tungsten?
WO3 + 3H2 —> W + 3H2O
Tungsten is reduced by…
Hydrogen
List three advantages of recycling scrap iron.
- This reduces the scrap iron in landfill sites.
- Scrap iron has already been extracted from its ore, it can also easily be separated from other material because it is magnetic.
- the process of melting scrap iron does not in itself produce carbon dioxide whereas extracting iron from its ore does.
List three advantages of recycling aluminium.
Recycled aluminium uses only about 5% of the enormous amount of energy used to extract aluminium from its ore.
Recycling avoids the production of large amounts of CO2.
For haloalkanes reactivity increases as we go….
Down the group as bond enthalpy is more important than bond polarity.
A nucleophile is either a….
Negatively charged ion or an atom with a delta minus charge.it has a lone (unshared) pair of electrons which it can use to form a covalent bond situated on an electronegative atom.
List some common nucleophiles…
The hydroxide ion -dot dot OH
Ammonia dot dot NH3
The cyanide ion - dot dot CN
Nucleophiles will…..
Replace the halogen in a haloalkane - nucleophilic substitution.
Write down the general equation for nucleophilic substitution.
Do it p188
In nucleophilic substitution what is the halide ion?
The leaving group
What are the conditions for nucleophilic substitution with sodium/potassium hydroxide?
Room temperature
Ethanol as solvent (haloalkanes don’t mix with water)
This is a hydrolysis reaction
An alcohol is formed
What are the products for nucleophilic substitution with cyanide ions?
The product is a nitrile the -CN is included in the root see page 189
One more carbon in the chain - useful.
What conditions are needed for ammonia to be a nucleophiles in neucleophilic substitution with a haloalkane?
Excess concentration of ammonia in ethanol under pressure. The reaction makes a primary amine.
Why is neucleophilic addition useful?
They are a way of introducing new functional groups into organic compounds.
Haloalkanes react by neucleophilic substitution an neucleophilic elimination but what dictates which one?
The conditions.
Why are elimination reaction useful?
It is a useful way of making molecules with carbon to carbon double bonds.
When is OH - ions in neucleophilic substitution?
Cold in aqueous
When is OH - ions in neucleophilic elimination?
Hot OH- in ethanol
What are chlorofluorocarbons?
Haloalkanes containing both chlorine and fluorine atoms but no hydrogen atoms (single bond).
What are short chain CFCs?
Gases - aerosols, refidgerants
Longer chain ones are used as dry cleaning solvents
