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Chemistry ✦ (Form 5) > Chpater 1 (1.5-1.6) > Flashcards

Chpater 1 (1.5-1.6) Flashcards

1
Q

What do metals typically exist as in nature

A

Metals usually exist as compounds or mixed with rocks and dirt.

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2
Q

What are compounds containing metals called

A

They are called ores or minerals and exist as metal oxides. metal sulphides. or metal carbonates.

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3
Q

Do non-reactive metals like gold and silver need to be extracted

A

No. they exist as metal elements and do not require extraction.

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4
Q

How are reactive metals like iron and aluminum extracted

A

They require specific methods based on their position in the reactivity series of metals.

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5
Q

What are the two common methods for extracting metals from ores

A

Electrolysis and reduction by carbon.

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6
Q

Which metals are extracted using electrolysis

A

Metals that are more reactive than carbon. such as aluminum.

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7
Q

Which metals are extracted by reduction with carbon

A

Metals that are less reactive than carbon. such as iron.

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8
Q

How is aluminum extracted from its ore

A

Aluminum is extracted using electrolysis after purifying bauxite to obtain aluminum oxide.

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9
Q

What is the role of cryolite in aluminum extraction

A

Cryolite lowers the melting point of aluminum oxide from 2000 °C. reducing energy consumption.

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10
Q

What reaction occurs at the anode during aluminum extraction. Oxidation:

A

2O2−(l)→O2(g)+4e−2O^{2-}(l) → O_2(g) + 4e^-.

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11
Q

What reaction occurs at the cathode during aluminum extraction. Reduction:

A

Al3+(l)+3e−→Al(l)Al^{3+}(l) + 3e^- → Al(l).

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12
Q

Why is aluminum extraction environmentally concerning

A

It consumes large amounts of electricity and produces carbon dioxide and toxic red sludge.

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13
Q

How is iron extracted from its ore

A

Iron is extracted using a blast furnace with carbon reduction.

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14
Q

What materials are added to a blast furnace

A

Iron ore (hematite). coke. and limestone.

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15
Q

What is the reaction in Zone 1 of the blast furnace

A

C(s)+O2(g)→CO2(g)C(s) + O_2(g) → CO_2(g). a redox exothermic reaction reaching 1600 °C.

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16
Q

What is the reaction in Zone 2 of the blast furnace

A

C(s)+CO2(g)→2CO(g)C(s) + CO_2(g) → 2CO(g)

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17
Q

What is the reaction in Zone 3 of the blast furnace

A

Iron(III) oxide is reduced: Fe2O3(s)+3CO(g)→2Fe(l)+3CO2(g)Fe_2O_3(s) + 3CO(g) → 2Fe(l) + 3CO_2(g).

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18
Q

What is the role of limestone in a blast furnace

A

Limestone decomposes to calcium oxide. which reacts with impurities to form slag.

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19
Q

Why is slag important in the blast furnace process

A

It separates impurities from molten iron and is less dense. allowing easy removal.

20
Q

What is a thermite reaction

A

A reaction where a more reactive metal (e.g. aluminum) reduces a less reactive metal oxide. producing molten metal.

21
Q

What is the thermite reaction equation for aluminum and iron(III) oxide

A

Fe2O3(s)+2Al(s)→Al2O3(s)+2Fe(l)Fe_2O_3(s) + 2Al(s) → Al_2O_3(s) + 2Fe(l).

22
Q

Why is the thermite reaction useful

A

It produces molten iron for welding railway tracks.

23
Q

How are metals like chromium and titanium extracted

A

By reduction using more reactive metals.

24
Q

What is the reactivity series of metals used for

A

Determining the best extraction method for metals based on their reactivity.

25
Q

Which metals are extracted directly by heating in air

A

Less reactive metals like copper and mercury.

26
Q

Which metals exist as elements and do not require extraction

A

Unreactive metals like silver and gold.

27
Q

What is rusting of iron

A

A type of metal corrosion that occurs when iron reacts with oxygen and water.

28
Q

What forms on the surface of iron during rusting

A

A layer of reddish-brown iron oxide that is easily cracked and permeable.

29
Q

Why does rusting continue once it starts

A

The iron oxide layer is permeable. This allows oxygen and water to reach the iron. This causes continuous damage.

30
Q

What conditions are needed for rusting

A

Oxygen gas and water.

31
Q

What are the main steps in the redox reaction of rusting

A

Oxidation. Reduction. Formation of a chemical cell. Formation of rust

32
Q

What happens during the oxidation step of rusting

A

Iron atoms release electrons to form iron(II) ions (Fe²⁺).

33
Q

What happens during the reduction step of rusting

A

Oxygen gas gains electrons and is reduced to form hydroxide ions (OH⁻).

34
Q

How is a chemical cell formed in rusting

A

Oxidation occurs at the negative terminal. Reduction occurs at the positive terminal. This creates a flow of electrons.

35
Q

What is the final product of rusting

A

Hydrated iron(III) hydroxide. This is also known as rust (Fe₂O₃·3H₂O).

36
Q

What is metal corrosion

A

The oxidation of metal due to air. This includes oxygen gas. water. and/or electrolytes.

37
Q

Which type of metal corrodes faster. more electropositive or less electropositive

A

More electropositive metals corrode faster.

38
Q

Why does iron corrode faster than copper

A

Iron is more electropositive than copper. This makes it easier to oxidize.

39
Q

How can using a more electropositive metal prevent corrosion

A

The more electropositive metal acts as a sacrificial layer. This is done by oxidizing and protecting the less reactive metal.

40
Q

What happens if a zinc-coated iron is scratched

A

Zinc

41
Q

How can using a less electropositive metal like tin prevent corrosion

A

The less electropositive metal forms a protective layer. If scratched. it accelerates iron’s corrosion instead of preventing it.

42
Q

What happens when tin-coated iron is scratched

A

Iron. being more electropositive than tin. oxidizes faster. This increases the rate of corrosion.

43
Q

How does rust form from iron(II) ions and hydroxide ions

A

Iron(II) ions react with hydroxide ions to form iron(II) hydroxide (Fe(OH)₂). This is further oxidized to iron(III) hydroxide (Fe(OH)₃).

44
Q

What is the final chemical formula for rust

A

Fe₂O₃·3H₂O. This is also known as hydrated iron(III) hydroxide.

45
Q

Why is rusting a problem for iron structures

A

Rust weakens the structure. This is because it is brittle and permeable. This allows the process to continue.

Chemistry ✦ (Form 5) (3 decks)

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