ONE-SCHOOL.NET Short Notes: Form 5 Chemistry

[Pages:15]ONE-

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 = (Product) (Time)

Rate of Reaction = (Product) (Time)



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Chemical Reaction

ONE-

Precipitation of Sulphur

2HCl(aq) + Na2S2O3(aq) 2NaCl(aq) + S(s) + SO2(g) + H2O(l)

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

Na2S2O3: Sodium thiosulphate

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)

(More detail in Form 4 Chapter 9)

2SO2 + O2 2SO3



2

Ostwald Process (Manufacture Nitric Acid)

ONE-

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 Dissolve in water

2NO(g) + O2(g) 2NO2(g) 3NO2(g) + H2O(l) 2HNO3(aq) + NO(g)

Alkane

Carbon Compound

Alkane

Combustion

Substitution Reaction

(Halogenation)

Complete Combustion

Incomplete Combustion

Combustion Complete combustion

Incomplete combustion

C2H6

+

7 2

O2

2CO2

+ 3H2O

C2H6 +

5 2

O2

2CO

+

3H2O

C2H6 +

3 2

O2

2C

+

3H2O



3

Substitution Reaction

ONE-

Alkene

Alkane

Craking

Alkene

Alcohol

Dehydration

Combustion

Addition Reaction

Polymerization

Complete Combustion

Incomplete Combustion

+ Bromine/Chlorine + Potassium

Manganate(VII) + Hydrogen + Hydrogen Halide + Steam

Preparation of Alkene

Cracking of Alkane Dehydration of Alchohol

2C4H10 CH4 + C2H4 + C2H6 + C3H6 C2H5OH + C2H4 + H2O



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Combustion: Complete combustion: Incomplete combustion

Addition Reaction: + Bromine:

ONE-

C2H4 + 3O2 2CO2 + 2H2O C2H4 + 2O2 2CO + 2H2O

C2H4 + O2 2C + 2H2O

+ Potassium Manganate(VII):

+ Hydrohen: + Hydrogen Halide:

(Catalyst: platinum/nickel)

+ Steam (H2O):

Polymerization

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

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



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