Ethene

Question 1

Purpose of glass wool?

Answer 1

Holds ethanol in place
Avoids wetting alluminium oxide
Soaks up ethanol

Question 2

Why is the glass wool added after ethanol?

Answer 2

To soak up ethanol completely

Question 3

Appearance of aluminium oxide?

Answer 3

White powder

Question 4

Two functions of aluminium oxide

Answer 4

Catalyst and dehydrating agent

Question 5

Term used to describe reaction

Answer 5

Elimination

Question 6

Why is ethanol not heated directly?

Answer 6

Alcohol will evaporate too quickly

Question 7

Precautions?

Answer 7

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

Question 8

What is suck back?

Answer 8

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

Question 9

How do you avoid suckback?

Answer 9

Remove delivery tube from water before heat is stopped

Question 10

Why do you do discard the first test tube?

Answer 10

Consists mainly of air that has been displaced

Question 11

What is unsaturation?

Answer 11

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

Question 12

Give two tests for unsaturation?

Answer 12

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

Question 13

Give an equation to show what happens with bromine water?

Answer 13

Whisjisj idk

Question 14

What happens when ethene is burned?

Answer 14

Clear luminous flame

Question 15

Equation for the combustion of ethene

Answer 15

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

Question 16

Two uses of ethene

Answer 16

Speed up ripening of fruit

Manufacturing of plastics

Question 17

Give the equation for the preparation of ethene

Answer 17

C2H5OH = C2H4 + H20

Question 18

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

Answer 18

When heat is removed

Question 19

Give one possible consequence of a suck back occurring

Answer 19

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

Question 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

Answer 20

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

Question 21

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

Answer 21

Bromine water [brown-colourless] UNSATURATION

Question 22

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

Answer 22

Glass wool