Chemistry notes form4

Topics: Oxygen, Chlorine, Ammonia Pages: 23 (1850 words) Published: October 21, 2013
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Short Notes: Form 5 Chemistry
Rate or Reaction
Calculation
Rate of Reaction (Average Rate)

Rates of reaction =

Quantity change of reactants/products
Total time for the reaction

If the quantity change is immeasurable

Rates of reaction =

1
Total time for the reaction

Find the Rate From a Graph
Average Rate

Rates At an Instant

The rate of reaction is equal to the slope of the graph The rate of reaction at an instant, t, is equal to the of quantity against time.
slope of tangent at that instant.

Rate of Reaction =

Δ(Product)
Δ(Time)

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Rate of Reaction =

1

Δ(Product)
Δ(Time)

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Chemical Reaction
Precipitation of Sulphur

2HCl(aq) + Na2S2O3(aq) ⎯→ 2NaCl(aq) + S(s) + SO2(g) + H2O(l) Na2S2O3: Sodium thiosulphate

Notes:
1. Yellow precipitate (sulphur) is formed.
2. The reaction is slow.

Potassium Dichromate (VI) with Ethanedioic Acid

Cr2O72- + 14H+ + 3C2O42- ⎯→ 6CO2 + 7H2O + 2Cr3+
Notes:
1. In the reaction, the orange colour of the solution
turns into green.

Cr2O72-: dichromate(VI) ion (Orange)
C2O42-: ethanedioate ion (Colourless)
Cr3+ : Chromium(III) ion (green)

Potassium Manganate(VII) with Ethanedioic Acid

2MnO4- + 16H+ + 5C2O42- ⎯→ 10CO2 + 8H2O + 2Mn2+
Notes:
1. Mn2+ is colourless
2. In the reaction, the purple colour of the solution
turns into colourless.

MnO4-: Manganate(VII) ion (Purple)
Mn2+: Manganese(II) ion colourless

Decomposition of Hydrogen Peroxide

2H2O2 - ⎯→ 2H2O + O2
Catalyst: manganese(IV) oxide(MnO2), Iron(III) oxide (Fe2O3), silver (Ag) Haber Process (Manufacture Ammonia)

N2 + 3H2 ⎯→ 2NH3
(More detail in Form 4 Chapter 9)
Contact Process(Manufacture Sulphuric Acid)

2SO2 + O2 ⎯→ 2SO3
(More detail in Form 4 Chapter 9)

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2

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Ostwald Process (Manufacture Nitric Acid)
Stage 1

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
Notes:
1. Temperature = 900oC
2. Pressure = 4-10 atm
3. Catalyse = Platinum (Pt)
Stage 2

2NO(g) + O2(g) → 2NO2(g)
Dissolve in water

3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g)

Carbon Compound
Alkane
Alkane

Substitution
Reaction
(Halogenation)

Combustion

Complete
Combustion

Incomplete
Combustion

Combustion
Complete combustion

C2H6 +

7
O2 ⎯⎯→ 2CO2 + 3H2O
2

Incomplete combustion
5
O2 ⎯⎯→ 2CO + 3H2O
2
3
C2H6 + O2 ⎯⎯→ 2C + 3H2O
2

C2H6 +

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3

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Substitution Reaction

Alkene
Alkane

Alcohol

Craking

Alkene

Combustion

Complete
Combustion

Dehydration

Addition Reaction

+ Bromine/Chlorine
+ Potassium
Manganate(VII)
+ Hydrogen
+ Hydrogen Halide
+ Steam

Incomplete
Combustion

Preparation of Alkene
Cracking of Alkane

2C4H10 ⎯→ CH4 + C2H4 + C2H6 + C3H6
Dehydration of Alchohol

C2H5OH + ⎯⎯→ C2H4 + H2O

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4

Polymerization

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Combustion:
Complete combustion:

C2H4 + 3O2 ⎯→ 2CO2 + 2H2O
Incomplete combustion

C2H4 + 2O2 ⎯→ 2CO + 2H2O
C2H4 + O2 ⎯→ 2C + 2H2O

Addition Reaction:
+ Bromine:

+ Potassium Manganate(VII):

+ Hydrohen:

(Catalyst: platinum/nickel)
+ Hydrogen Halide:

+ Steam (H2O):

(Catalyst: phosphoric acid; Temperature: 300oC; Pressure: 60atm) Polymerization

(Catalyst: oxygen; Temperature: 200oC; Pressure: 1200atm)
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5

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Alcohol
Carbohydrate

Alkene

Alcohol

fermentation

Combustion

dehydration

Addition

+ Sodium

Oxidation
(+K2CrO7/KMnO4)

Preparation of alchohol
Fermentation of Carbohydrate (Glucose)

C6H12O6 ⎯⎯→ 2C2H5OH + 2CO2

Addition of Alkene

C2H4 + H2O ⎯⎯→ C2H5OH
[Catalyst:Phosphoric acid; Temperature:300oC; Pressure: 60atm ] or
C2H4 + H2SO4 ⎯⎯→ CH3CH2OSO3H
CH3CH2OSO3H + H2O ⎯⎯→ CH3CH2OH + H2SO4
Combustion of Alcohol

C2H5OH + 3O2 ⎯⎯→ 2CO2 + 3H2O...
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