Obtaining and using metals Flashcards
properties of more reactive metals: (2)
-more vigorous reactions
-easily loses electrons in reactions to form positive ions (cations)
what is formed when a metal reacts with water?
Metal + water → metal hydroxide + hydrogen
what is formed when a metal reacts with steam?
-how does it usually react with cold water?
Metal + steam → metal oxide + hydrogen
-metals that react slowly with cold water can react quickly with steam
what will a metal below hydrogen on the reactivity series NOT do?
react with dilute acids.
what happens in the reactions of metals with water, steam and acids? (2)
-metals lose electrons and form cations.
-metal is oxidised and the water is reduced.
how can you predict a metal’s relative tendency to form cations and its resistance to oxidation? (2)
the higher up a metal, the greater the tendency to form cations
the lower down a metal, the greater its resistance to oxidation
how does displacement occur in solutions?
a more reactive metal can displace a less reactive metal from its compounds.
how can a reactivity series be deduced? (3)
-by carrying out several displacement reactions.
-piece of metal is dipped into a salt solution.
-different combinations of metal and salt solution are tested
Explain why three combinations of metal and salt solution were not done in the investigation? (for deducing reactivity) (2)
-a metal cannot displace itself from a solution of one of its salts.
-there would be no reaction (so these combinations were not done)
what are redox reactions?
when reduction and oxidation happen at the same time,
what is an ore?
a rock that contains a metal or a metal compound
difference between low-grade and high-grade ores: (2)
-low-grade ores contain a small percentage of the metal or its compound
-high-grade ores contain a larger percentage
why is it wasteful to extract metal from low-grade ores?
expensive for a small amount of metal
how are metals extracted if they are LESS reactive or MORE reactive then carbon? (2)
less reactive than carbon:
-it can be extracted from its compounds by heating with carbon.
more reactive than carbon:
-electrolysis
what is formed when a metal oxide reacts with carbon?
Metal oxide + carbon → metal + carbon dioxide
how and why can be extract iron? (3)
-below carbon in the reactivity series it can be displaced from its compounds by heating with carbon.
-iron is extracted from iron ore in a large container called a blast furnace.
-iron(III) oxide is reduced to molten iron when it reacts with carbon
why is aluminium more expensive than carbon even though it is ore abundant in the Earth’s crust?
large amounts of electrical energy used in the extraction process.
why does aluminium need to be molten in order to be extracted? (3)
-what problem could arise from this?
-aluminium oxide is insoluble in water, so it must be molten to act as an electrolyte.
-melting point of aluminium oxide is high.
-lots of energy must be transferred to break its strong ionic bonds = expensive
how could we reduce the costs from melting aluminium oxide? (2)
-powdered aluminium oxide is dissolved in molten cryolite.
-this ionic compound melts at a lower temperature than aluminium oxide, reducing costs.
what happens during the electrolysis of aluminium oxide? (2)
-cathode = aluminium ions gain electrons and form aluminium atoms
-anode = oxide ions lose electrons and form oxygen gas
why must the electrodes used in separating aluminium oxide be changed? (3)
-oxygen reacts with the carbon anodes, forming carbon dioxide.
-the anodes gradually wear away and must be replaced frequently,
-adding to the cost of producing aluminium
Explain, with the help of a half equation, how oxide ions are oxidised during the electrolysis of aluminium oxide.
2O⁻² - 4e-. → O₂
Explain, with the help of a half equation, how aluminium ions are reduced during the electrolysis of aluminium oxide.
Al³⁺ + 3e- → Al
what does recycling a metal involve?
collecting used metal items and producing new metal from them.
