C7 Chemistry Revision Additional Science U1

-Family of hydrocarbons  - Compounds in fuels (natural gas, petrol) 

- Don't dissolve in water/ immiscible with water (LESS DENSE THAN WATER) 

- Gases at room temperature 

- Burn in air: combustion products are carbon dioxide and water

Methane + oxygen -----> carbon dioxide + water 

CH4 + 2O2 -----> CO2 + 2H2O

- Do NOT react with common aqueous reagents because C-C AND C-H bonds are generally UNreactive

Name Molecular formula 

methane CH4 | ethane C2H6 | propane C3H8 | butane C4H10 | pentane C5H12

    -  Liquids

-OH FUNCTIONAL GROUP (reactive part of alcohol molecule) 

Ethanol: best known member of the alcohols (Y) 

- Present in beer, wine  - Useful Solvent  - Lotions and perfumes  - HIGHLY FLAMMABLE 

 STRONGER INTERMOLLECULAR BONDS THAN ALKANES: Liquids

(strong attractive forces between molecules) 

- misscible with water because OH group is similar to water 

- long chained hydrocarbons ( C7H15OH) IMMISCIBLE -long chain doesn't interact with water: oiliness dominates :( 

ethanol + oxygen ->  carbon dioxide + water | C2H5OH + 3O2 -> 2CO2 + 3H2O

sodium + ethanol -> sodium ethoxide + hydrogen | 2Na + 2C2H5OH -> 2C2H5ONa + H2

1) sodium + methanol --> sodium methoxide + hydrogen

2Na + 2CH3OH --> 2CH3OHNa + H2

2) sodium + propanol --> sodium propoxide + hydrogen

2Na + 2C3H7OH --> 2C3H7ONa + H2  

3) sodium + water -> sodium hydroxide + hydrogen

Na + H2O -> NaOH + H2

      -COOH Functional Group      - Weak acids 

- Acetic acid (ethanoic) : main acid in vinegar : preserves and flavours a range of foods

Citric acid: gives oranges and lemons sharp taste

Lactic acid: forms in muscle cells during exercise and milk as it turns sour 

Some carboxylic acids smell and taste bad  (butanoic acid in rancid butter and vomit smell)

Methanoic acid HCOOH        Ethanoic acid CH3COOH         

1) ethanoic acid + sodium -> sodium ethanoate + hydrogen 

2) methanoic acid + sodium hydroxide -> sodium methanoate + water

3)  ethanoic acid + calcium carbonate -> calcium ethanoate + carbon dioxide + water  

     - COO Functional group - smells and flavours of fruits 

• flavour foods 
• make sweet smelling perfumes, shampoos and bubble baths 
• As solvents 
• As plasticizers to make polymers like PVC soft and flexible 

Esters:alcohol and carboxylic acid ---> ester and water: ___yl         _____anoate 

                                                                                     alcohol ^      carboxylic acid ^

ethanoic acid + methanol -> methyl ethanoate + water 

FATS AND OILS - energy stores for animals and plants 

 - glycerol ( the alcohol in fats and oils) - fatty acids (carboxylic acids in fats and oils) 

Animal Fats (butter and lard) - solid   - single bonds (C-C)  SATURATED 

no hydrogen atoms can be added    - tightly packed together/ regular shape 

Vegetable Oils (sunflower oil) - liquid    - double bonds (C=C) UNSATURATED 

more hydrogen atoms can be added    - more difficult to pack together molecules 

-immiscible with water   - can be a lubricant   - ester + water -> acid + alcohol

stages in the laboratory preparation of ethyl ethanoate

Ethyl ethanoate (ethyl acetate) is an ester. The equation for preparing an ester is: ‘acid + alcohol → ester + water’ (reversible reaction).

Ethanoic acid + ethanol  ethyl ethanoate + water  

Safety: - Goggles    - Gloves    - Fume Cupboard   - Lab Coat 

1) Place ethanol and pure ethanoic acid into a round bottomed flask with sulfuric acid (catalyst- speeds up reaction) then heat under reflux condenser so the liquid doesn't evaporate. 

2) Distil off the ester with a condenser so the impure product is separated from the reaction mixture after refluxing. 

3) Use a separating funnel to shake the impure ester with aqueous reagents (sodium carbonate) to remove impurities. The ester layer can be tapped off from the separating funnel for purification. 

4) The drying agent (anhydrous calcium carbonate) helps to remove more impurities.  

5) Bumping granules help mixture boil smoothly.Use distillation to ensure a pure dried ester is formed. 

Refluxing: ensures the reaction occurs the fastest at highest possible reaction temperature, the boiling point of the mixture. Condenser is used to prevent vapour loss when boiling, the vapourised liquids are condensed back into the reaction flask.

Distillation: To separate the ester from the other chemicals in the flask. 

Purification: The organic layer separated in the separating funnel to leave the pure ester.  

Drying: The use of anhydrous (without water) calcium chloride solution to remove impurities

Ester: To form an acid you must add an alcohol to a carboxylic acid. 

E.g. Carboxylic acid + Alcohol -> Ester + Water

Butanoic acid +Propanol -> Propyl Butanoate + Water