Section 4

Physical Chemistry

3d) Ethanol

This whole section is for Paper Two:

Manufacture of Ethanol by Ethene and Steam (H₂O):  

-C₂H₄ + H₂O  C₂H₅OH
-hydration- exothermic
-300C and 60-70 atm
-phosphoric acid catalyst
-un-reacted ethene recycled

fast reaction 
pure ethanol
continuous 

non-renewable resources 
energy needed to make steam 

Manufacture of Ethanol from Fertilisation: 

-C₆H₁₂O₆ -----> 2C₂H₅OH + 2CO₂
-anaerobic respiration
-exothermic reaction
-20-60 hrs

-30-40C
-purified by fractional distillation

renewable resources 
organic waste material 

impure ethanol due to water 
slow process
only 15% ethanol in each batch 

Dehydration of Ethanol to Ethene:

Ethanol    ------> Water and Ethene 

C₂H₅OH ------>  H₂O  and C₂H4 

3c) Alkenes

• general formula - CnH2n
• double bond - unsaturated 

Ethene		C2H4
Propene		C3H6
Butene		C4H8

Butene Isomers:

Isomers have the same molecular formula,but a different structural formula 

Commonly represented as:

Methylpropene:

Addition reaction of alkenes and bromine

Test for C = C, Add Bromine water
It turns from orange to colourless

3b) Alkanes

• Single covalent bonds of hydrocarbon 
• General formula of CnH2n+2

Name	Displayed formula	Molecular formula
Methane		CH4
Ethane		C2H6
Propane		C3H8
Butane		C4H10
Pentane		C5H12

Isomers- different structures 

• Butane 
• Methylpropane 

Complete and Incomplete combustion:

Complete: Alkane and Oxygen -----> Carbon dioxide and water
                    CH4   and   2O2     ---->          CO2          and 2H2O

Incomplete: Carbon monoxide- C3H8 + 3.5O2 -----> 3CO + 4H2O
                     Carbon (soot)- C3H8 + 2O2 -----> 3C + 4H2O

Methane Substituion Reaction /w Halogen
CH4 + Br2 ---UV Light---> CH3Br + HBr  

3a) Introduction

Homologous series ----------> - have same general formula
                                                - successive members differ by CH4
                                                - similar chemical reactions
                                                - tread in physical properties --> boiling and melting points

Hydrocarbon -----------> compound made up of only carbon and hydrogen

Saturated: no double bonds
Unsaturated: double bonds

Isomerism: Referring to isomers which are molecules that have the same molecules but have different displayed formulas.

Section 3

Organic Chemistry

2g) Tests for ions and gases

Flame tests for metal ions:

• dip in HCl
• Heat in flame 
• Clean
• dip in crystals 
• place on burnsen burner flame 
• identify colour 

+-------------+-----------+---------------------+
| Metal ions  |           | Flame test colour   |
+-------------+-----------+---------------------+
| Li+         | Lithium   | Brick red/ Crimson  |
+-------------+-----------+---------------------+
| Na+         | Sodium    | Yellow              |
+-------------+-----------+---------------------+
| K+          | Potassium | Purple/Lilac        |
+-------------+-----------+---------------------+
| Ca3+        | Calcium   | Brick red           |
+-------------+-----------+---------------------+

Tests for gases

+--------------------+------------------------+----------------------------+
| Hydrogen H2        | Light                  | Burns with a 'squeaky pop' |
+--------------------+------------------------+----------------------------+
| Oxygen O2          | glowing splint         | Relights                   |
+--------------------+------------------------+----------------------------+
| Carbon Dioxide CO2 | Limewater              | Makes it go cloudy/milky   |
+--------------------+------------------------+----------------------------+
| Ammonia NH3        | Damp red litmus paper  | turns blue                 |
+--------------------+------------------------+----------------------------+
| Chlorine Cl2       | Damp blue litmus paper | turns red                  |
+--------------------+------------------------+----------------------------+

Tests for cations:

+------+---------------+----------------------------------------+
| NH4+ | Add NaOH (aq) | NH3 released;test --> damp red litmus  |
|      |               | paper goes blue                        |
+------+---------------+----------------------------------------+

+-------+-----------+------------------------+
| Cu2+  | Add NaOH  | Pale blue precipitate  |
+-------+-----------+------------------------+
|       | Cu2+(aq) + 2OH-(aq) --> Cu(OH)2(s) |
+-------+------------------------------------+

+-------+-----------+-------------------------+
| Fe2+  | Add NaOH  | Dirty green precipitate |
+-------+-----------+-------------------------+
|       | Fe2+(aq) + 2OH-(aq) --> Fe(OH)2(s)  |
+-------+-------------------------------------+

+-------+------------+-----------------------+
| Fe3+  | Add NaOH   | Red-brown precipitate |
+-------+------------+-----------------------+
|       | Fe3+(aq) + 3OH-(aq) --> Fe(OH)3(s) |
+-------+------------------------------------+

Tests for anions:

+-------+-------------------------------+-------------+
| Ion   |                               | Precipitate |
+-------+-------------------------------+-------------+
| Cl-   | dilute nitric acid. Add AgNO3 | white       |
+-------+-------------------------------+-------------+
|       |        Ag+(aq) + Cl-(aq) --> AgCl(s)        |
+-------+---------------------------------------------+
| Br-   | dilute nitric acid. Add AgNO3 | cream       |
+-------+-------------------------------+-------------+
|       |        Ag+(aq) + Br-(aq) --> BrAg(s)        |
+-------+---------------------------------------------+
| I-    | dilute nitric acid. Add AgNO3 | yellow      |
+-------+-------------------------------+-------------+
|       |         Ag+(aq) + I-(aq) --> AgI(s)         |
+-------+---------------------------------------------+
| SO42- | Acidify with HCL. Add BaCl2   | white       |
+-------+-------------------------------+-------------+
|       |      Ba2+(aq) + SO42-(aq) --> BaSO4(s)      |
+-------+---------------------------------------------+
| CO32- | Add acid, CO2 is released.    | milky       |
|       | Bubble through limewater      |             |
+-------+-------------------------------+-------------+