Chemistry 5070 · O Level · Alkenes

Alkenes — practice question

This item concerns alkanes and alkenes.
(a)[2]

But-1-ene is part of the alkene homologous series. Consecutive members of the same homologous series differ by a -CH$_2$- group and show similar chemical properties. State two other features of a homologous series.

(b(i))[1]

Explain how Fig. 4.1 indicates that but-1-ene is an unsaturated compound.

(b(ii))[1]

Give the structural formula for but-1-ene.

(b(iii))[1]

Draw the displayed formula for an isomer of but-1-ene.

(c(i))[1]

Undecane, $\text{C}_{11}\text{H}_{24}$, occurs in the kerosene/paraffin fraction obtained when petroleum is distilled. Give one use for the kerosene/paraffin fraction.

(c(ii))[2]

When undecane is cracked, smaller hydrocarbon molecules are produced. Construct the symbol equation for a reaction in which undecane is cracked and the only products are butane, propene and ethene.

(d(i))[1]

Propane reacts with chlorine to make chloropropane and one additional product, X. $\text{C}_3\text{H}_8 + \text{Cl}_2 \rightarrow \text{C}_3\text{H}_7\text{Cl} + X$ Name product X.

(d(ii))[1]

State the essential condition for this reaction.

(e(i))[3]

Ethene reacts with bromine at room temperature. Calculate the enthalpy change for this reaction in kJ/mol. Use the bond energies in Table 4.1.

(e(ii))[1]

Describe the colour change seen when excess ethene is added to a few drops of aqueous bromine. from …………………… to ……………………

Worked solution & mark scheme

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