Prepare ethene and examine its properties

Draw a diagram of this experiment

…

Step 1

Set up apparatus as shown and light the Bunsen burner. Ethanol changes into a vapour and is dehydrated over the aluminium oxide to form ethene

Draw a diagram of this experiment

…

Step 1

Set up apparatus as shown and light the Bunsen burner. Ethanol changes into a vapour and is dehydrated over the aluminium oxide to form ethene

Step 2

Allow bubbles to escape for a while. Raise apparatus so that the delivery tube is no longer in the water and turn off the Bunsen burner

What would happen if the delivery tube was left in water?

Suck-back

Why is suck-back not good?

Causes apparatus to crack or explode

Features of ethene gas

Colourless with a sweetish smell. Insoluble in water but soluble in cyclohexane or chloroform

Three methods for testing for ethene

Combustion. Addition of bromine. Addition of acidified KMnO4

Combustion (3)

Hold a lighted taper to the mouth of the test tube. Gas burns with a luminous flame. Add limewater and shake the test tube, it should turn milky

Addition of bromine (1)

If bromine water is added to ethene the red colour disappears and becomes colourless.

Acidified KMnO4 (2)

Add a small amount of very dilute KMnO4 to a test tube of ethene. Colour changes from purple to colourless

Ethene combustion formula

C2H4 + 3O2 → 2CO2 + 2H2O