Chemistry 0620 · IGCSE · Alkenes

Alkenes — practice question

Ethene is an alkene, and it reacts with bromine, as the equation below shows. $\text{C}_2\text{H}_4 + \text{Br}_2 \rightarrow \text{C}_2\text{H}_4\text{Br}_2$
(a)[1]

State the general formula for alkenes.

(b)[1]

Describe the colour change observed when ethene is bubbled through aqueous bromine. from ................. to .................

(c)[1]

In this reaction, a single product is made from two reactants. Name this type of organic reaction.

(d(i))[3]

The reaction is exothermic. Complete the energy profile diagram for this reaction. Include: • where the products should be placed • an arrow showing the activation energy, labelled as A • an arrow showing the energy change for the reaction.

(d(ii))[3]

Use the bond energies in the table to calculate the energy change in this reaction. Follow these steps. • Work out the energy required to break bonds. • Work out the energy released when bonds are made. • Calculate the energy change in this reaction.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: $\text{C}_n\text{H}_{2n}$

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