C7: Metals Flashcards
Physical properties of metals
A -common to all metals
- good conductors of electricity
- good conductors of heat
- malleable
- ductile
- lustrous(shiny)
- solids at room temperature
B - transition metals
- high melting and boiling points
- sonorous
- high density
- hard
exceptions to physical properties of metals
- group 1 metals have low denisty and are soft
- tin and lead are fairly soft.
- mercury is a liquid at rtp
- copper is pinkish brown in colour when freshly cut
Chemical Properties of metals
- react with oxygen to form oxides
- react with water if above hydrogen in the electrochemical series
- react with dilute acids to form salt and hydrogen gas.
which metals do not react with oxygen?
metals low in the elctrochemical series eg gold
metals higher in the electrochemical series react with water to form__________
a metal hydroxide + hydrogen
which metals do not react with dilute acids?
those that are below hydrogen in the electrochemical series
why is it that calcium and sodium are never used to react with acids in the school lab?
the reaction can be very explosive
reactive metals lower in the electrochemical series react with hot water or steam to form__________
metal oxide and hydrogen
metal oxide + dilute acid gives:
salt + water
metal hydroxide + dilute acid gives (1)________. This type of reaction is called a (2)_____________
- salt + water
- neutralization reaction
metal cabonate + dilute acid gives
salt + water + carbon dioxide
heat + group 1 metal nitrate ===>
metal nitrite + oxygen
Heat + metal nitrate(except group 1) ——>
metal oxide + nitrogen dioxide + oxygen
If the nitrate of an unreactive metal is heated the products are:
unreactive metal + nitrogen dioxide + oxygen
a metal nitrate is heated and only oxygen gas is given off. From which goup is the metal?
group 1
a metal nitrate is heated and a brown gas is seen + the pure metal remains. Where is the metal in the reactivity series?
very low and below hydrogen
metal nitrate + heat ——> metal oxide + NO2 + O2
Where whould the metal be in the reactivity series?
above hydrogen and below the group 1 metals
when a compound is broken down by heat
thermal decomposition
group 1 carbonate(except lithium) + heat —–>
no reaction
carbonate(not group 1) + heat ——>
metal oxide + carbon dioxide
which metal carbonates do not decompose on heating? what is the exception?
group 1
exception - lithium carbonate
group 1 (except lithium) metal hydroxide + heat ——>
no reaction
metal oxide + heat —->
no reaction , except a few unreactive metal oxides such as silver oxide.
the nitrates and carbonatesof (1)______________ metals undergo thermal decoomposition more easily than those of (2)______________ metals
- less reactive
- more reactive
relationship between the reducing power of a metal and its position in the electrochemical series
the higher in the electrochemical series, the greater reducing power and vice versa.
what is meant by the reducing power of a metal?
ability to give away electrons (remember OIL RIG)
Metals that are (1)_____________ in the reactivity series are (2)_______________ reactive and therefore give away electrons (3)__________ to become (4)_____________. A more reactive metal will (5)___________ a less reactive metal form its (6)___________ by (7)_____________ it.
- higher
- more
- easily
- cations
- displace
- salt/compound
- reducing
In the following pairs say if the metal on the right will displace the one on the left:
- Zn(s) + Cu2+(aq) ——>
- Mg(s) + Zn2+ ———–>
- Ca(s) + Al3+————–>
- Ag(s) + Cu2+ ———–>
- Pb(s) + Al3+ —————>
- yes
- yes
- yes
- no
- no
How is thermal decomposition of carbonates, nitrates and hydroxides related to the electrochemical or reactivity series?
the ease of decomposition increases down the reactivity series. compounds of sodium and potassium are stable or only decompose slightly(nitrates)
where is carbon in reactivity series
between aluminium and zinc
what is the reactivity series of metals based on?
- how vigorous the metals react with dilute acids
- how easily metal compounds undergo thermal decomposition
- whether or not a metal will displace another metal from its compounds
On going up the reactivity series, the ability to give away electrons (1)____________ , therefore the metal becomes a stronger (2)____________, and forms compounds that are more (3)____________, because their (4) ______________ are more stable.
- more easily
- reducing
- stable
- ions
Method of extraction of metals depends on:
Position of the metal in the electrochemical series
extraction of metals above carbon in the electrochemical series
Electrolysis of their molten ores
Extraction of metals below carbon (zinc and below)
Reduction by heating with a reducing agent such as carbon
reducing agents used in extracting metals
Carbon, carbon monoxide, hydrogen
which metals require more energy to extract from their ores and why?
- Aluminium and above
- because they form very stable compounds and as such eletrolysis in needed to extract them and this process requires large amounts of energy
Main methods of extraction of metals
- direct physical separation from the earths crust
- electrolysis
- reduction
suggest a method for the extraction of each metal below
- gold
- aluminium
- iron
- silver
- direct physical separation
- electrolysis
- reduction
- direct physical separation
the extraction of metals from their ores is a ________________ process
reduction
what are the 2 ores of aluminium?
- impure hydrated aluminium oxide(bauxite)
- sodium aluminium fluoride , Na3AlF
Label the diagram of the electrolytic cell for the extractio of aluminium
W - graphite anode (+)
R - Cathode(-)
V - Molten aluminium oxide(alumina)
P - Molten Aluminium
what is alumina?
pure anhydrous aluminium oxide
why is alumina dissolved in cryolite?
- reduces the melting temperature of alumina and energy required to melt it.
- the mixture is a better conductor than alumina by itself
what are the products of the electrolysis of alumina?
cathode: aluminium ions reduced to aluminium
anode: oxide ions oxidized to exygen gas
what happens to the aluminium that is formed at the cathode?
it collects at the bottom of the electrolytic cell and is tapped off
the chemical formula or cryolite?
Na3AlF6
what is the use of cryolite in the extraction of Al?
reduce melting point and increase conuctivity of molten Al2O3
overall reaction for the electrolysis of Aluminium Oxide:
2Al2O3 =====> 4Al + 3O2
what kind of electrodes are use in the extraction of aluminium?
graphite
what happens at the cathode during the electrolysis of aluminium oxide?
what is the half equation?
Aluminium ions reduced to elemental aluminium
half equation: Al3+(l) + 3e ======> Al(l)
what happens at the anode during the electrolysis of aluminium oxide?
what is the half equation?
Oxide ions oxidised to oxygen gas
half equation: 2O2- (l)====> O2(g) + 4e
what are the ores of iron?
- haematite - impure iron(III) oxide - Fe2O3
- magnetite - impure iron(II, III) oxide - Fe3O4
what are the raw materials used in the extraction of iron?
iron ore, coke, limestone and air
Name of the structure used to exract iron
blast furnace
General equation for the reduction of iron from its ore
Fe2O3(s) + 3CO(g) ====> 2Fe(l) + 3CO2(g)
ldentify the different substances in the diagram of the blast furnace
M - mixture of metal ore (haematite), coke and limestone
G - gas waste
X - hot air
Y - slag (calcium silicate)
Z - molten iron
what reaction takes place in each zone. Show equations for the reactions
Zone 1: Hot air reacts with carbon(coke) to form CO2:
C(s) + Os(g) ===> CO2(g)
Zone 2: CO2 reacts with Carbon to form CO:
CO2(g) + C(s) ====> 2CO(g)
Zone 3: CO reduces Iron Odixe to iron:
Fe2O3(s) + 3CO(g) ====> 2Fe(l) + 3CO2(g)
Role of limestone in the extraction of iron
limestone is added to the blaast furnace to remove the main impurity in the iron ore, Silicon dioxide. The reaction produces liquid calcium silicate(slag) which is tapped off.
reaction between limestone and silicon dioxide to form calcium silicate(slag)
the reacion comprises two stages:
- Thermal decomposition of limestone to form Calium Oxide and CO2:
CaCO3(s) ===> CaO(s) + CO2(g)
- Reaction betweeen CaO and Silicon dioxide to form calcium silicate:
CaO(s) + SiO(g) ===> CaSiO3(l)
what is slag used for?
- an ingredient in cement production
- mixed with asphalt to build roads
- used as aggregate in concrete for construction
Uses of aluminium
- overhead electrical cables
- window frames and doors
- cans to store drinks
- cooking utensils
- aluminium foil
uses of lead
- making car batteries
- soldering
- joining metal pipes
- radiation shields eg Xray shield
- Keel for sailboats
- lead weights eg fishing and diving weights
uses of iron
- pure iron too weak to be useful. instead it is mixed with other metals to form steel alloys
- making car bodies
- contruction
- making aircraft
- makinf food and drink cans
- tools
- surgical instruments
- indistrial chemical vessels
what is an alloy?
Mixture of two or more metals or mixture of one or more metals with a non-metal such as carbon.
examples of iron alloys and their uses
- stainles steel - surgical iinstruments, cooking utensils, sinks.
- mild steel - construction of bridges, oil rigs, ships, trains and motor vehicles, tin cans coated with tin.
- high carbon steel - cutting tools such as chisels, knives, dril bits, masonry nails
- cast iron - engine parts, railings, gates, manhole covers, hinges and cast iron cookware
examples and uses of aluminium alloys
- Duraluminum - aircraft construction, bodies of motor vehicles
- Magnalium - aircraft and motor vehicle parts
why are alloys sometimes stronger and harder than the metals from which they are made?
The regular metal lattice is disrupted by the presence of different sized atoms present in an alloy. Therefore the layers cannot slide over each other so easily. this makes the metal alloy stronger and/or harder
List some toxic metals and the damage they can cause
lead: -
- damages body tissues and organs
- harms nervous system especially in childre leading to low IQ
- interferes with production
Arsenic-
- Damages the skin
- causes skin cancer
Mercury - damages nervous system leading to problems with coordination, hearind gloss, impaired vision and speech - Minamata disease
Cadmium -
- weakens bones leading to oteoporosis
- damages the kidneys, liver and lungs
How do toxic metals harm the evironment?
- improper disposal of waste containing heavy metals is a major source of pollution.
- Think bioaccumlation. As the toxic metal moves up the food chain its concentration in the rganism increases thereby increasng its toxic effects
- Heavy metals remain in the environment for a long time
- Toxic metals can reach underground water and contaminate water sources
- Toxic metals can be inhaled such as from car exhausts, burning of fossil fuels such as coal.
list some useful metals
magnesium - important for plants to make chlorophyll in order to carry out photosynthesis
Iron - important for animals to produce haemoglobin in order to carry oxygen needed for respiration
Calcium - imporant for forming healthy bones and teeth of animals
Zinc - important for growth and repair of tissues as well the normal functioning of the immune sytem.
Sodium and potassium - important for the transmission of nerve impulses and for muscles t contract
Difference between corrosion and rusting
corrosion is the gradual dissolving away of a metal from its surface inwards. rusting is a special form of corrosion where iron(III) oxide is formed from the reaction between iron and oxygen in the presence of water.
