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Flashcards in Ethene Deck (22):
1

Purpose of glass wool?

Holds ethanol in place
Avoids wetting alluminium oxide
Soaks up ethanol

2

Why is the glass wool added after ethanol?

To soak up ethanol completely

3

Appearance of aluminium oxide?

White powder

4

Two functions of aluminium oxide

Catalyst and dehydrating agent

5

Term used to describe reaction

Elimination

6

Why is ethanol not heated directly?

Alcohol will evaporate too quickly

7

Precautions?

Keep ethanol away from flame - flammable
Remove delivery tube from water before you stop heating to prevent suck back
Avoid inhaling glass wool

8

What is suck back?

Air inside the boiling tube contracts which gives rise to a partial vacuum

9

How do you avoid suckback?

Remove delivery tube from water before heat is stopped

10

Why do you do discard the first test tube?

Consists mainly of air that has been displaced

11

What is unsaturation?

When a compound has carbon carbon double/triple bonds and does not contain the max amount of hydrogens it can contain

12

Give two tests for unsaturation?

Bromine water is added by drops to the test tube of gas. The test tube is stoppered and shaken - brown/red to colourless
Saturated - no colour change
Acidified kMnO4 - purple to colourless

13

Give an equation to show what happens with bromine water?

Whisjisj idk

14

What happens when ethene is burned?

Clear luminous flame

15

Equation for the combustion of ethene

C2h4 + 3O2 = 2CO2 + 2H20 and heat

16

Two uses of ethene

Speed up ripening of fruit
Manufacturing of plastics

17

Give the equation for the preparation of ethene

C2H5OH = C2H4 + H20

18

At what stage is “suck back” most likely to occur?

When heat is removed

19

Give one possible consequence of a suck back occurring

Air inside boiling tube contracts as it cools - cold water is sucked into test tube and test tube cracks

20

Assuming this percentage yield of 60%, what is the maximum number of 75cm^3 test tubes of ethene gas that could be collected at room temperature and pressure when 2.4cm^3 of ethanol and density 0.8g\cm^3 react?
exam papers - 2012

multiply density by volume to get mass of ethanol
divide by mr of ethanol to get moles
using mole hopping, moles of ethanol = moles of ethene
multiply by mr of ethene to get grams
use formula - % yield = actual yield
theoretical yield x100
multiply by ROOM TEMP = 24,000cm
and divide by the 75cm^3 test tubes

21

Describe a chemical test to distinguish between samples of ethene and ethene

Bromine water [brown-colourless] UNSATURATION

22

Identify the solid which is used to keep the ethanol at the end of the test tube

Glass wool