This is a simple way of making gaseous alkenes like ethene. If ethanol vapour is passed over heated aluminium oxide powder, the ethanol is essentially cracked to give ethene and water vapour.
b) Using sulphuric acid at a temperature of 170°C.
Concentrated sulphuric acid produces messy results. Not only is it an acid, but it is also a strong oxidising agent. It oxidises some of the alcohol to carbon dioxide and at the same time is reduced itself to sulphur dioxide.
Both of these gases have to be removed from the alkene. It also reacts with alcohol to produce a mass of carbon. There are other side reactions as well.
Option D is correct.
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