Required practical 5a

Question 1

Step 1

Answer 1

Add 20cm3 cyclohexanol into 50cm3 pear shaped flask which has been weighed

Question 2

How to calculate accurate mass of cyclohexanol

Answer 2

Reweigh the pear shaped flask

Question 3

Step 2

Answer 3

Use a graduated dropping pipette to add 8cm3 phophoric acid to the flask

Question 4

What should be done during the addition of phosphoric acid

Answer 4

Shake the flask continuously

Question 5

Step 3

Answer 5

Add a few anti bumping granules to the flask and set up semi-micro distillation apparatus with liebig condensor

Question 6

What is the role of anti bumping granules

Answer 6

Prevent the formation of large bubbles

Question 7

Why is distillation used

Answer 7

Cyclohexene has a lower boiling point (83) then cyclohexanol (162)

Question 8

Step 4

Answer 8

Heat the mixture gently to distil off any liquids that boil below 100 degrees

Question 9

Why should a Bunsen not be used

Answer 9

Organic liquids are flammable

Question 10

Step 5

Answer 10

Pour the distillate into separating funnel and add 50cm3 of saturated sodium chloride solution

Question 11

What is the role of the saturated sodium chloride

Answer 11

Drying agent

Question 12

What should be done after the addition of Sodium chloride and why

Answer 12

Shake the funnel to allow the layers to separate

Question 13

Step 6

Answer 13

Carefully run of the more dense aqueous layer into a beaker, and then transfer the remaining, less dense organic layer into a small conical flask

Question 14

Step 7

Answer 14

Add a few lumps of anhydrous calcium chloride to remove water and shake

Question 15

What is the role of the anhydrous calcium chloride

Answer 15

Drying agent

Question 16

What should be done after the addition of the anhydrous calcium chloride

Answer 16

Leave the liquid to stand until it becomes clear

Question 17

Step 8

Answer 17

Decant the liquid into a dry, clean sample container which has been weighed

Question 18

How to calculate accurate mass of Cyclohexene produced

Answer 18

Reweigh the sample container

Question 19

What can be found with the accurate mass of cyclohexene produced

Answer 19

Percentage yield

Question 20

How to test for the presence of alkene

Answer 20

1. Add 1cm3 distillate to test tube
2. Add 1cm3 bromine water to test tube
   –> Presence of alkene should decolourise bromine water (orange to colourless)