Chemistry practical = cracking

Question 1

Aim of this experiment

Answer 1

Catalytic cracking of long chain alkanes to shorter chain ones and alkenes

Question 2

Step 1

Answer 2

Place mineral wool into boiling tube

Question 3

Step 2

Answer 3

Add 2cm3 liquid paraffin into boiling tube so soaks into mineral wool
Remove excess paraffin

Question 4

Step 3

Answer 4

Clamp boiling tube at the mouth at an angle

Question 5

Step 4

Answer 5

Add aluminosilicate catalyst into tube
Ensure doesn’t fall to the bottom and touch the mineral wool and paraffin

Question 6

What is good about the aluminosilicate in the middle of the tube?

Answer 6

Open structure so large surface area for reaction to take place on

Question 7

Step 5

Answer 7

Attach bung with delivery tube to mouth of tube into a bowl of water with test tubes in water

Question 8

Step 6

Answer 8

Use Bunsen flame to heat the catalyst stone
Briefly heat the paraffin

Question 9

Step 7

Answer 9

Collect gas in test tube until many tubes are collected

Question 10

Why is it important to always keep boiling tube hot?

Answer 10

By cooling, water may be sucked back into the boiling tube and then crack
So when finishing, remove from water first and ensure no water droplets are in the delivery tube and continue heating

Question 11

Why is the boiling tube clamped at an angle?

Answer 11

To avoid the catalyst mixing with the paraffin

Question 12

Why is the catalyst heated instead of the hydrocarbon?

Answer 12

Because then it would have evaporated without cracking