Chemistry - C10 Metals

Know that aluminium is extracted from the ore bauxite by electrolysis

Extraction by electrolysis (including aluminium) ○ Metals that are more reactive than carbon e.g aluminium are extracted by electrolysis of molten compounds. ○ Metals that react with carbon can be extracted by electrolysis as well

Describe and explain the essential reactions in the extraction of iron from hematite in the blast furnace, including the removal of acidic impurities as slag C + O2 -> CO2 C + CO2 -> 2CO Fe2O3 + 3CO -> 2Fe + 3CO2 CaCO3 -> CaO + CO2 CaO + SiO2 -> CaSiO3

In the blast furnace (very high temperatures) iron oxide is reduced with carbon: ● Iron ore, coke and limestone are added into a blast furnace ● Hot air enters from bottom and goes to top of furnace ● Oxygen reacts with coke to form CO2, which reacts again with coke to form CO ● CO is a reducing agent, turning iron oxide into iron ● Some carbon will also reduce the iron oxide to iron ● Molten iron runs to the bottom of the furnace and then runs off An ore is a rock from which metals can be extracted. The main ore of iron is hematite, which contains large amounts of iron(III)oxide. It is reduced by carbon to for iron, but this takes place in a huge blast furnace. The raw materials needed to do this are hematite, coke, limestone and air. The hematite, coke and limestone are added at the top of the furnace. A strong current of hot air is blown in at the bottom of the furnace. It is hot enough to react with the coke. At the bottom of the furnace, the coke burns in the hot air blast to form carbon dioxide. This is an exothermic reaction and the heat released keeps the furnace hot. C(s) + O2(g) ———-> CO2(g) The carbon dioxide produced reacts with the coke to form carbon monoxide: CO2(g) + C(s) ———-> 2CO(g) This carbon monoxide reduces the iron(III) oxide to iron: Fe2O3(s) + 3CO(g) ———-> 2Fe(l) + 3CO2(g) Most of the iron is produced this way and flows to the bottom of the furnace and is removed from time to time. In hotter parts of the furnace, the carbon itself can directly reduce the iron: Fe2O3(s) + 3C(g) ———-> 2Fe(l) + 3CO2(g) (To memorise this series of equation, just remember that coke turns to carbon-dioxide which turns to carbon monoxide which then reduces the iron). Why is the limestone added? The hematite contains other impurities like sand (silicon(IV)oxide). The limestone (calcium carbonate-CaCO3) helps remove these impurities. The heat from the furnace decomposes the limestone: CaCO3(s) ———-> CaO(s) + CO2(g) The calcium oxide produced reacts with the silicon(IV)oxide to form a 'slag' of calcium silicate. This slag is used as a building material, especially in road building. CaO(s) + SiO2(l) ————> CaSiO3(l)

Describe the use of carbon in the extraction of some metals from their ores

Metals below carbon in the reactivity series can be extracted using carbon. Carbon reduces the the metal oxides that are extracted, when heated. Example: lead(II)oxide + carbon (coke/coal) —————-> lead + carbon monoxide The carbon in the form of coke (which is coal fro which impurities have been removed) has reduced the lead by removing the oxygen from it to produce lead. Carbon monoxide can also be used as a reducing agent. Example: zinc oxide + carbon monoxide ————> zinc + carbon dioxide The second to last element in the reactivity series is gold, since it is very unreactive, it is found in the Earth as the metal itself ● But, most metals are found as compounds that require chemical reactions to extract the metal ● Metals less reactive than carbon: o Can be extracted from their oxides by reduction with carbon o Don't forget: reduction involves the loss of oxygen

Describe the general physical properties of metals as solids with high melting and boiling points, malleable and good conductors of heat and electricity

Metals have giant structures of atoms with strong metallic bonding. o Therefore, most metals have high melting and boiling points. o They can conduct heat and electricity because of the delocalised electrons in their structures. o The layers of atoms in metals are able to slide over each other, so metals can be bent and shaped. (malleable)

Explain in terms of their properties why alloys are used instead of pure metals

Pure metals have a regular arrangement of rows of equally sized positive metal ions surrounded by a sea of delocalised electrons. Because the ions are arranged regularly and are equal in size, the layers are able to slide over each other easily, leaving metals being soft and malleable ● Alloys are made from 2 or more different types of metals. The different sized atoms distort the layers in the structure, making it harder for them to slide over each other. So alloys are harder than pure metals. When a metal is alloyed with a second metal, the different sized metal atoms make the arrangement of the lattice less regular. This stops the layers of metal atoms from sliding easily over each other when a force is applied. Thus an alloy is stronger and harder than a pure metal. This is why alloys are used rather than metals for industrial uses. One very common alloy is the brass. It is an alloy made of copper and zinc. It is stronger than copper but still malleable, so is used in making musical instruments and ornaments. Another very common alloy is stainless steel, made from iron, chromium and nickel. Iron rusts easily but the alloy doesn't, so it can be used to make car parts, cutlery, surgical instruments etc.

Relate the method of extraction of a metal from its ore to its position in the reactivity series for the metals listed in section 10.2 and for other metals, given information

The way we extract a metal from its ore depends on the position of the metal in the reactivity series. Carbon is used to reduce oxides of metals below it in the reactivity series. Metals above carbon in the reactivity series cannot be extracted from their oxides by heating with carbon. This is because the metal bonds to oxygen too strongly and the carbon is not reactive enough to remove it. So we have to use electrolysis to extract metals more reactive than carbon, such as aluminium, magnesium and calcium.

Place in order of reactivity: potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen) and copper, by reference to the reactions, if any, of the elements with: - Water or steam - Dilute hydrochloric acid - Reduction of their oxides with carbon

We can put metals in order of their reactivity by investigating how well they react with water or hydrochloric acid. Reaction of metals and hydrogen with water or steam: The reaction of metals and hydrogen with dilute (hydrochloric) acid: We can see that the above elements are put in their order of reactivity- the more reactive on the top (potassium, sodium, calcium etc) and the least reactive on the bottom (iron, hydrogen, copper). Only metals above hydrogen will react with water/steam and hydrochloric acid. This is the reactivity series, from most reactive to least reactive (and a mnemonic to remember it!) : Metals can be arranged in order of their reactivity in a reactivity series o Metals potassium, sodium, calcium, magnesium, zinc, iron and copper can be put in order of their reactivity from their reactions with water and dilute acids o Non-metals hydrogen and carbon are often included in the reactivity series

Describe the reactivity series in terms of the tendency of a metal to form its positive ion, illustrated by its reaction, if any, with: - Aqueous ions of other listed metals - The oxides of the other listed metals

When metals react with other substances, metal atoms form positive ions ● Reactivity of a metal is related to its tendency to form positive ions ● A more reactive metal can displace a less reactive metals from a compound e.g. oxide or aqueous solution with the aqueous ions (think about how this is similar as well to halogens) Previosuly, we saw that a more reactive halogen will replace a less reactive halogen in a metal halide. We can see this is a competition to see which halogen combines best with the metal. We call this type of a reaction a displacement reaction. Metals can also 'compete' in a similar way. Iron(III) oxide + aluminium ———-> iron + aluminium oxide In the above, reaction the aluminium displaced the iron (think of it as 'the aluminium stole the oxide and the iron was left alone'). This happened because aluminium is higher in the reactivity series than iron i.e. aluminium is more reactive than iron. Let's take another example, with an aqueous solution, and see how the metal ions form: zinc + Copper(II)sulfate ———-> zinc sulfate + copper Zn(s) + CoSO4(aq) ———————> ZnSO4(aq) + Cu(s) Here, the zinc, being the more reactive metal, has clearly displaced copper to form zinc sulfate Let's break it up into half equations: Zn(s) - 2e- ———-> Zn2+(aq) the zinc oxidised (lost electrons) Cu2+(aq) + 2e- ———-> Cu(s) the copper reduced (gained electrons) We can see that the more reactive metal, zinc, has lost electrons and the less reactive metal, copper, has gained electrons. The more reactive a metal is, the more easily it loses its valence electrons. It is easier to lose valence electrons and thus be more reactive, if: the valence electrons are further away from the nucleus. When they are farther away, the attraction of these electrons (negative charge) to the protons (positive charge)in the nucleus will be reduced. So it is easier to 'let go' of the electrons. there are more electron shells between the nucleus and the valence electrons. These shells shield the valence electrons from the charge of the nucleus (protons). there are fewer protons in the nucleus (less charge) to pull the electrons towards them Zinc is more reactive than copper because its valence electrons are farther away from the nucleus and it has more shells. Zinc has more protons than copper but the other two conditions outweigh this one. So overall, zinc finds it easier to lose its valence electrons than copper, and so is more reactive, and thus can displace copper.

Deduce an order of reactivity from a given set of experimental results

use the results from either reactions written on the reactivity series or action of heat on metal hydroxides/nitrates/carbonates. ● generally, less reactive metals will remain unchanged as they will not undergo reaction When displacement reaction equations is given, you should be able to put them in order of reactivity. Just remember that the metal that displaces the other one is the more reactive one.