chemistry 2.2

Question 1

What are the two chemical processes by which ethanol can be made?

Answer 1

Fermentation of sugars

Hydration of ethene

Question 2

How is ethanol manufactured by the hydration of ethene ?

Answer 2

• Using steam in the presence of a phosphoric acid catalyst
• carried out at 300 degrees and 60 atm
• reversible so incomplete…95% conversion rate

Question 3

How is fermentation used to make ethanol?

Answer 3

• Starch or sugar converted into ethanol and CO2
• catalyst in yeast called zymase
• done at 37degrees
• above 37 the enzyme is denatured

Question 4

What limits the conversion of sugars to ethanol

Answer 4

Toxicity of alcohol as above 14% denatures enzyme

Done in the absence of air as anaerobic

Question 5

Give some uses of ethanol other than alcohol

Answer 5

• perfume
• methylated spirits
• mixed with petroleum as fuel
• cleaning fluids

Question 6

How are spirits made from ethanol?

Answer 6

• heated alcohol-water mixture to distill
• alcohol boils off faster than water and is moved to be condensed
• distillate higher alcohol content than liquid

Question 7

What are methylated spirits used for and how are they made?

Answer 7

• fuel in spirit burners and camping stoves
• removing paint or ink stains
• made by adding methanol to ethanol and dye; makes it toxic and undrinkable

Question 8

Defined volatility

Answer 8

The ease for a liquid to turn into a gas which increases with a smaller boiling point

Question 9

Why do alcohols dissolve in water?

Answer 9

Because hydrogen bonds form between the polar OH groups of the alcohol and water molecules

Question 10

Why does solubility decrease as the chain length increases

Answer 10

A larger part of the alchohol molecule is made up of a non polar hydrocarbon chain
Hydrocarbon chain does not form hbonds with water molecules

Question 11

How would you classify a primary alcohol
How would you classify a secondary alcohol
How would you classify a tertiary alcohol

Answer 11

• OH group is attached to a carbon atom with no or one alkyl group
• OH group is attached to a carbon with 2 alkly groups
• OH group attached to a carbon bonded to 3 alkyl groups

Question 12

What is a suitable oxidising agent and how can it be made

Answer 12

• a solution with acidified dichromate ions

- made by mixing potassium dichromate and sulfuric acid

Question 13

What do primary alcohols oxidise to

Answer 13

gentle heating = aldehyde

stronger heating = carboxylic acid

Question 14

Define reflux

Answer 14

continual boiling and condensing of a reaction mixture to make sure the flask does not boil dry while the reaction is taking place

Question 15

What do secondary alchohols oxidise to form

Answer 15

ketones

Question 16

What colour does acidified dichromate change to when successfully oxidised

Answer 16

orange to green

Question 17

Define esterification

Answer 17

the reaction of an alchohol with a carboxylic acid to form and ester and water

Question 18

How would you prepare an ester

Answer 18

• Put 1cm3 of an alchohol and 1cm3 of a carboxylic acid in a boiling tube and add a few drops of H2SO4
• put the boiling tube in water bath of 80 degrees for 5 minutes
• when done put the boiling tube in a cold water bath and the oil that floats on top is the ester

Question 19

Define dehydration

Answer 19

an elimination reaction where a water molecule is removed from a saturated molecule to make a unsaturated molecule

Question 20

What are some uses of halogenoalkanes

Answer 20

organic sythesis
used to prepare many useful materials
aerosol cans

Question 21

Why do halogenoalkanes contain a polar carbon-halogen bond

Answer 21

• because they have different electronegativities
• the carbon atom is less electronegative than the halogen atom so the bonded pair is more attracted to the halogen atom
• this = polar bond

Question 22

Define hydrolysis

Answer 22

the reaction of water or aqueous hydroxide to break a chemical compound into two new compounds

Question 23

What do curly arrows respresent

Answer 23

the movement of an electron pair

Question 24

LOOK OVER 2.2.6

Answer 24

NOW

Question 25

What are the properties of polytetraflouroethane and what can it do

Answer 25

strong carbon-fluorine bonds = resistance to chemical attacks
heat resistant
electrical insulator
non stick qualities SO can be used to coat pots and pans or metal surfaces
also used as nail polish

Question 26

What are some uses of PVC

Answer 26

drainpipes
plastic window frames
childrens toys
packaging

Question 27

Why were CFC’s first developed

Answer 27

refrigerant gases in the 1800’s were fatal when people breathed in the fumes so freon developed CFC’s as an alternative

Question 28

How do CFC’s affect the ozone layer

Answer 28

stable until they reach stratosphere where they absorb ultraviolet radiation to form chlorine radicals which break down the ozone

Question 29

What are some alternatives to CFC’s

Answer 29

hydroflouroalkanes and hydroflourohydrocarbons

Question 30

how do you work out percentage yield normally and applied to moles

Answer 30

actual yield/predicted yield

actual mole/theoretical mole

Question 31

how to work out atom economy

Answer 31

molecular mass of desired product/sum of molecular mass of all products

Question 32

what reactions have an atom economy of 100%

Answer 32

addition reactions