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Metals
Characteristics, reactivity, extraction, uses and impact
| Question | Answer |
|---|---|
| Define metallic bonding. | The strong electrostatic force of attraction among metal cations and their delocalized sea of electrons within the lattice structure of the same metal. NB. This occurs within the bulk of one metal itself. |
| List 6 physical properties of metals. | 1) High melting and boiling point 2) Good thermal and electrical conduction 3) Shiny appearance 4) High malleability 5) Ductility 6) High density |
| List 3 chemical properties of metals. | 1) They form cations (positive ions) by losing their valence electrons. 2) They react with non-metals to form ionic compounds. 3) They are reducing agents since they give their electrons to the other reactant. |
| metal + oxygen -> | metal oxide |
| metal + water -> | metal hydroxide + hydrogen gas |
| metal + steam -> | metal oxide + hydrogen gas |
| reactive metal + acid -> | salt + hydrogen gas |
| List the reactivity series of metals from most to least reactive. | K, Na, Ca, Mg, Al, (C), Zn, Fe, Sn, Pb, (H), Cu, Ag, Au, Pt |
| T or F. All acids contain hydrogen ions (H+). | T |
| State the formula for hydrochloric acid. | HCl (aq) |
| State the formula for hydrogen chloride gas. | HCl (g) |
| State the formula for sulphuric acid. | H2SO4 |
| State the formula for sulphurous acid. | H2SO3 |
| State the formula for nitric acid. | HNO3 |
| State the formula for nitrous acid. | HN02 |
| State the formula for phosphoric acid. | H3PO4 |
| State the formula for carbonic acid. | H2CO3 |
| metal oxide + acid -> | salt + water |
| metal hydroxide + acid -> | salt + water |
| metal carbonate + acid -> | salt + water + carbon dioxide |
| T or F. The hydroxides and carbonates of K and Na are thermally stable and do not decompose upon heating. | T |
| What happens to the nitrates of K and Na when heated? | They decompose slightly to form metal nitrite and oxygen gas. |
| What happens to the hydroxides of the metals from Ca to Cu on the reactivity series when heated? | They decompose to form metal oxide and steam (water vapour H2O (g)) |
| What happens to the carbonates of the metals from Ca to Cu on the reactivity series when heated? | They decompose to form metal oxide and carbon dioxide gas. |
| What happens to the nitrates of the metals from Ca to Cu on the reactivity series when heated? | They decompose to form metal oxide, nitrogen dioxide and oxygen gas. |
| T or F. The hydroxides and carbonates of Ag metal are too unstable to exist. | T |
| What happens to the AgNO3 when it is heated? | It decomposes to form silver, nitrogen dioxide and oxygen gas. |
| Why do very reactive metals form very stable compounds? | Very reactive metals greatly desire to bond in order to achieve stability. Once they have bonded, it becomes very difficult to separate/displace them from their compound. |
| Why do very unreactive metals form very unstable compounds? | Very unreactive metals are already relatively stable. If and when they bond, it is easier to separate/displace them from their compound since they prefer existing by themselves. |
| State one use of Zn metal and the property upon which it is based. | -Coating for other metals such as Fe (galvanizing) -Zinc forms a protective layer of zinc oxide which is stable to air. |
| State one use of Pb metal and the property upon which it is based. | - Protective cases for radioactive substances. - Pb absorbs radioactive emissions. |
| State one use of Fe metal and the property upon which it is based. | - Railings, pipes, cars, bridges, engine tools - Strong and malleable |
| State one use of Cu metal and the property upon which it is based. | - Electrical cables, coinage, radiators - Good conductor of heat and electricity, relatively unreactive |
| State one use of Al metal and the property upon which it is based. | - Cooking utensils, electrical cables, aluminium foil - Good conductor of heat and electricity, forms a beneficial, protective oxide layer when it corrodes. |
| State one use of Mg metal and the property upon which it is based. | - Manufacture of alloys used in aircrafts, engines, flares, fireworks etc. - Light, malleable, does not corrode. Burns with a brilliant white flame. |
| What are alloys? | Mixtures of metals (and sometimes non-metals) which are miscible when molten and do not separate when cooled. They have more advantageous properties than their individual constituents. |
| Describe the components of brass alloy and the advantages of the alloy over individual constituents. | Cu and Zn (Copper and Zinc) Harder, stronger and more malleable than copper. |
| Describe the components of solder alloy and the advantages of the alloy over individual constituents. | 50% Sn and 50% Pb (Tin and Lead) Sn gives it a lower melting point; Pb makes it harder. The alloy melts easily and flows readily over clean metal surface. |
| Describe the components of duralumin alloy and the advantages of the alloy over individual constituents. | 95% Al, 4% Cu, traces of Mg and Mn. Aluminium makes it light. The other metals make it stronger than Al. It is used in aircraft construction. |
| Describe the components of steel alloy and the advantages of the alloy over individual constituents. | Fe and 1-5% C + Cr/Ni/W/Mn/Co depending on type of steel. Cr (chromium) makes steel more resistant to corrosion W (tungsten) or Mn (manganese) makes steel harder for the use in cutting tools and drills Co (cobalt) makes steel a permanent magnet |
| Describe the components of magnalium alloy and the advantages of the alloy over individual constituents. | 5% Magnesium 95% Aluminium Stronger than either metal alone, resistant to corrosion, malleable, ductile etc. Used to make aircraft parts. |
| What is an ore? | Naturally occurring compounds (impure ionic compounds) which contain metals e.g. metal oxides, sulfides and carbonates. |
| T or F. The extraction of a metal from its ore is a reduction process. | T |
| State, with reason, the method used to extract metals high in the reactivity series from their ores. | Electrolysis of the molten ore -These metals form very stable ions (when they react to form compounds) therefore it is very difficult to remove them (from their ores) by reduction. |
| State, with reason, the method used to extract metals low in the reactivity series from their ores. | Heating the ore with reducing agent such as carbon - These metals form less stable ions (when they react) therefore they are easily removed from their ores by reduction. |
| Name the ore of aluminium. | Bauxite i.e. impure, hydrated aluminum oxide (Al2O3.xH2O) |
| Name the two ores of iron. | Haematite i.e. impure iron (III) oxide (Fe2O3) Magnetite i.e. impure iron (II, III) oxide (Fe3O4) - this is a mixed oxide containing both iron II and iron III so the formula represents the sum of both formulae ( FeO + Fe2O3 = Fe3O4) |
| Iron is extracted from its ore in a blast furnace. List 4 raw materials which are required for the process. | -Iron ore (usually haematite Fe2O3) -Coke (carbon) -Limestone (calcium carbonate) - Air (oxygen) |
| What is the function of coke(carbon) in a blast furnace? | Burns in air to produce heat and reacts to form carbon monoxide (which is needed to reduce the iron oxide) |
| What is the function of limestone in a blast furnace? | Helps remove acidic impurities from the iron by reacting with them to form molten slag( calcium silicate CaSiO3). |
| What is the function of air in a blast furnace? | Allows the coke (carbon) to burn and so produces heat. |
| Iron (III) oxide + carbon -> 2Fe2O3 (s) + 3C (s) -> | iron + carbon dioxide 4Fe (l) + 3CO2 (g) |
| Iron(III) + carbon monoxide -> Fe2O3 (s) + 3CO (s) -> | iron + carbon dioxide 2Fe (l) + 3CO2 (g) |
| Thermal decomposition of CaCO3 (s) -> | CaO (s) + CO2 (g) |
| calcium oxide + silica -> CaO (s) + SiO2 (s) -> | calcium silicate CaSiO3 (l) |
| T or F. The removal of silica from haematite is a neutralization reaction since calcium oxide is basic and silica is acidic. | T |
| Aluminium is the most abundant metal in the Earth's crust. Why is the extraction process very expensive? | Large amounts of electricity are required to extract it by the process of electrolysis. |
| Why does Al2O3 need to be melted before electrolysis can occur? | The ions need to be mobile. |
| The melting point of Al2O3 is over 2000 degrees C. Name the substance in which it is dissolved to lower its melting point. | Molten cryolite |
| The negative electrode is called a | cathode |
| The positive electrode in called an | anode |
| What happens to Al3+ cations during electrolysis of Al2O3? | The gains electrons from the cathode and form molten aluminium (Al (l)) |
| What happens to the O2- anions during electrolysis of Al2O3? | They lose electrons at the anode and form oxygen molecules (O2 (g)). |
| Define corrosion. | Th gradual wearing away of the surface of a metal by reacting with chemicals in the environment, mainly oxygen and water vapour. It is an oxidation process. |
| T or F. In general, the higher a metal is in the reactivity series, the faster it corrodes. | T |
| Why is the corrosion of Al beneficial? | When fresh Al is exposed to air, it immediately forms a layer of aluminium oxide (Al2O3).This layer adheres to the metal surface, does not flake off and is relatively unreactive. It therefore protects the aluminium from further corrosion |
| Why is the corrosion of Fe detrimental? | When iron and steel objects are exposed to oxygen and moisture, they corrode to form rust. Rust does not adhere to the iron below, it flakes off instead. This exposes fresh iron to oxygen and moisture, which then rusts and the rust flakes off. |
| Define rusting. | The corrosion of iron and steel to form hydrated iron (III) oxide (Fe2O3.XH2O - rust). |
| What are macrominerals? | These are required by the body in relatively large quantities ( over 100 mg per day) These include calcium, potassium, sodium and magnesium. |
| What are microminerals (trace minerals)? | These are requires in much smaller quantities. These include iron, zinc, cobalt, manganese, copper, molybdenum, selenium and chromium. |
| What are organometallic compounds? | These are organic (carbon based) compounds whose molecules contain metal ions. E.g. haemoglobin (contains Fe) and chlorophyll (contains Mg) |
| What is the result of Mg deficiency in plants? | Yellowing of leaves (chlorosis) |
| What is the result of iron deficiency in humans? | Iron-deficiency anaemia: reduced red blood cell count, reduced oxygen transport, tiredness and reduced energy. |
| State the importance of Ca in humans. | Essential to produce calcium hydroxyapatite in the bones and teeth. Calcium deficiency leads to rickets in children and osteoporosis in adults. |
| State the importance of Zn in humans. | Important in the functioning of the immune system, for wounds to heal, and for the growth and repair of cells and tissues. |
| State the importance of Na and K in humans. | Important for impulses to be transmitted along nerves and for muscles to contract. |
| What are heavy metals ? | High density metals which are toxic even at low concentrations. Eg lead, arsenic, cadmium, mercury |
| Name one source and effect of lead pollution. | - discarded lead acid batteries - particularly harmful to young children as it can reduce IQ, cause behavioural problems and learning disorders. |
| Name one source and effect of arsenic pollution. | - mining of metals such as gold, volcanic eruptions - damages to nervous system, heart, lungs and blood vessels, cancer, thickening of skin |
| Name one source and effect of cadmium pollution. | - discarded nickel-cadmium batteries - can cause bone to become weakened and fragile leading to osteoporosis, damages to respiratory system if inhaled. |
| Name one source and effect of mercury pollution. | - discarded fluorescent light bulbs - results in loss of muscular coordination, numbness in hands and feet, impaired hearing, sight and speech – this condition is known as Minamata disease. |
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CSEC Chemistry 10th Grade
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