Other important addition reactions of alkenes
2 marks · EasyExplain, with reference to the products formed, why the reactions of ethene with hydrogen and with steam are both called addition reactions.
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Must show: Reactant(s) add across double bond, One product formed from two reactants
Common mistakes: Stating 'it is a reaction' without mentioning addition of atoms; Not referring to type or number of products
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Marking points
B1 · 1 mark · States that the reactant molecules add to ethene at the double bond.
B2 · 1 mark · Explains only one product is formed from two reactants.
Worked solution
Both reactions are called addition reactions because atoms from the other reactant (hydrogen or water) add across the double bond in ethene. In each case, two reactants combine to form a single product.