C7 Reactivity

C7 Reactivity

Reduction and Oxidation

Oxidation Is Loss Reduction Is Gain

Reduction is : 1. Loss of oxygen (covalent bonds)

2. gain of electron (ionic)

The reduced compound is an oxidizing agent

Oxidation is : 1. Gain of oxygen (covalent bonds)

2. loss of electron (ionic)

The oxidized compound is a reducing agent

 

Reactivity with Oxygen

Oxidation reactions – Cu + O2 → CuO, glow + slice flame

Mg + O2 → MgO white flames

Combustion reactions – CnHn + O2 → water + CO2 flames and stuff

 

Reactivity series

K←Na←Li←Ca←Mg←Al←C←Zn←Fe←H←Cu←Ag←Au

Possibly nicer livers can magnetize almonds cars,

zero-fee hype cures silvery golds

 

Metal extraction

Ore is economically viable containing metal rocks. Rock contains metals but not that worthwhile.

1. If metal ore is less reactive than carbon…
   1. Reduce metal with carbon to extract.
2. If it is more reactive
   1. Use electrolysis to split ions.

Alloys are formed to merge several desirable qualities of the different metals. Since lattice structure is disrupted by impurities, boiling point decreases as bonds are weaker.

 

Electrolysis

Electricity pass through electrodes to extract metals. Cations are at cathode and anions go to anode. Electrolyte is the solution that conducts electricity.

Half equations:

Cations: Pb2+ + 2e– → Pb

AnionsL 2Cl– → Cl2 + 2e–

1. 1. Separating seawater: Aqueous sodium hydroxide, hydrogen at cathode and chlorine at anode, sodium hydroxide is leftover – liquid NaCl won’t have leftovers.
   2. Industrial uses include: chlorine for swimming pool disinfectant and cleaning products, sodium hydroxide for stock chemical (strong alkali) and soap, hydrogen for haber process and margarine.
   3. Separating aluminum oxide: Al2O3, aluminum ore called bauxite, can be used to extract aluminum which is lightweight resistant to corrosion and used in airplane and bikes. Cryolite added to lower melting point. Al sinks to the bottom, produces aluminum and oxygen.

 

• molten lead(II) bromide, lead at cathode and bromine at anode

• aqueous copper chloride – copper at cathode and chlorine at anode

• dilute sulfuric acid – hydrogen at cathode and oxygen at anode

• Generally: metals or hydrogen form at cathode and non-metals form at anode.

 

Electrodes can be active or inert. Inert electrodes like graphite are not involved in the reaction and actibe electrodes are involved in reaction. Such as copper plating. Anode will become thinner and cathode thicker, and hence it is used to plate objects and remove impurity, electrolyte usually contains the same ion as anode.

Hoffman Voltameter is used to collect gas from electrolysis, such as water.

 

Blast furnace

Used to extract iron.

1. Add materials: hematite, coke(impure carbon as reducing agent), limestone to remove impurities
2. Make the reducing agent stronger: Carbon must become carbon monoxide
   1. C + O2 → CO2
   2. CO2 + C → CO
3. Reduce the iron:
   1. Fe2O3 + 3CO → 2Fe + 3CO2,
4. Remove impurities
   1. CaCO3 → CaO + CO2
   2. CaO + SiO2 (sand) → CaSiO3 (slag, used in road building, neutralizsation reaction)
5. 1000C and 2000C degrees

 

Rust

Rust is the specific corrosion of iron by oxidation to iron (3) oxide. Salt speeds up rusting and both oxygen and water are needed to produce hydrated iron oxide in a redox reaction.

Surface protection means covering iron to stop water/oxygen from entering, using oil, paint and wax. Specifically, galvanizing means coating with zinc.

Sacrificial protection puts a metal attachment of metals more reactive than iron like zinc and magnesium so water and air reacts with it first.

C6 Detective Chemistry

C6 Detective Chemistry

Testing for water

1. Add anhydrous copper sulfate (will turn from white to blue)
2. Use cobalt chloride paper (will turn from blue to pink)

Purification of water

Water is purified

1. First by filtration, to remove any insoluble particles, being sprayed onto specially prepared layers of sand and gravel. As it trickles through, different sized insoluble solids are removed. The filter beds are cleaned periodically by pumping clean water backwards through the filter.
2. Second by chlorination to kill any bacteria.

Uses of water

1. Industry: becoming a chemical solvent, use in cosmetics and food, etc
2. Home: drinking, bathing, cooking, etc

Separating gases in air

1. 1. Cool air into a liquid.
   2. Heat gradually and use fractional distillation to separate gases at their different boiling points.

 

• Nitrogen has the lowest boiling point, hence it is collected first.

 

Test for gases

Oxygen	Will relight a glowing splint.
Hydrogen	Burning splint goes out/explodes with a squeaky pop
CO2	Bubble through limewater, will form white precipitate
Ammonia	Turns damp red litmus → blue (due to alkalinity)
Chlorine	Turns blue litmus red and ultimately bleaches it (due to acidity)

Flame tests

1. Put clean wire into HCl.
2. Dip wire into solid you want to test.
3. Hold wire in flame.

Sodium will burn yellow, potassium will burn lilac, copper will burn green.

 

Test for cations

 

	Sodium hydroxide (aq)	Ammonium hydroxide (aq)
Ammonium (NH4+)	Ammonia gas upon warming with NaOH, will turn damp red litmus paper blue. basic.	N/A
Copper (II) Cu2+	Light blue ppt insoluble	Dark blue ppt soluble
Iron (II) Fe2+	Green ppt insoluble in excess
Iron (III)Fe3+	Red/brownish ppt insoluble in excess
Zinc (II) Zi2+	White ppt soluble in excess turns colorless

 

Test for anions – white precipitates

	Acidification and reaction
Carbonate (CO32-)	Add HCl which produces CO2 and water. Bubble through limewater for white precipitate.
Chloride (Cl–)	Acidify with nitric acid, then react with silver nitrate White precipitate purple in sunlight, silver chloride insoluble
Sulphate (SO42-)	Acidify with HCl and react with barium chloride White insoluble barium sulphate ppt
Nitrates (NO3–)	Reduce nitrates into ammonia first Use aluminum catalyst to test for ammonia.

 

Methods of separating mixtures

1. 1. Filtration for insoluble solid and liquid. Filter through paper to separate filtrate from insoluble residue.

 

• Crystallization for soluble compounds and saturated solutions. Evaporate one product and find the other product left in the basin.

• Chromatography for separating soluble mixtures of liquids using difference in solubility.

• Distillation for separating soluble liquids through difference in boiling point. Both vapor and liquid can be collected. Vapor can be condensed.

• Fractional distillation for separating more than one liquids at different boiling points at different columns.