IB Chemistry HL 1.2.1 Bond energies Question Bank

Practise IB Chemistry HL 1.2.1 by applying bond energies to exam-style questions.

[Maximum number: 4]

Organic compounds have many industrial applications.

(a)

Ethene reacts with steam to produce ethanol.

\mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g}) \rightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{~g})

[ 4 ]

(i)

Calculate the enthalpy, in kJ , of the reaction using section 12 of the data booklet.

[ 3 ]

ALTERNATIVE 1:

Bonds broken:

$1 \mathrm{C}=\mathrm{C}+4 \mathrm{C}-\mathrm{H}+2 \mathrm{O}-\mathrm{H} / 614+4(414)+2(463) / 3196$ «kJ»

Bonds formed:

1 C-C+1 C-O+5 C-H+1 O-H /

346+358+5(414)+463 /

3237 «kJ»
$\Delta H=\text { «3196-3237 }=\text { » }-41 \text { «kJ» » }$

ALTERNATIVE 2:

Bonds broken:
$1 \mathrm{C}=\mathrm{C}+1 \mathrm{O}-\mathrm{H} / 614+463 /$

1077 «kJ»

Bonds formed:
$\begin{aligned} & 1 \mathrm{C}-\mathrm{C}+1 \mathrm{C}-\mathrm{O}+1 \mathrm{C}-\mathrm{H} / 346+358+414 / & 1118\langle\mathrm{~kJ}\rangle{ }^{2} & \Delta H=\langle 1077-1118=\rangle-41\left\langle\mathrm{~kJ} \|{ }^{2} \right. \end{aligned}$

Award [3] for correct final answer.

Award [2 max] for +41 «kJ».

(ii)

Outline why the enthalpies calculated in (i) and (ii) are different.

[ 1 ]

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1.2.1—Bond energies question 1

Question (a)

Question (i)

Question (ii)