IB Chemistry HL 2.3.1 Dynamic Equilibrium Questions

Use real HL exam questions to define and identify dynamic equilibrium in physical and chemical systems, including rate and phase evidence.

Exam points

Define dynamic equilibrium as equal forward and reverse reaction rates in a closed system.
Identify a physical or homogeneous chemical equilibrium from equal opposing rates, phase relationships and unchanged macroscopic composition.
Explain why a reaction or titration must be controlled quickly or at low temperature to limit an unwanted equilibrium shift or hydrolysis.

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Study 2.3.1—Dynamic equilibrium conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 3]

Nitrous acid, $\mathrm{HNO}_{2}$ , is a weak acid which can be used to make acidic buffers.

(a)

The overall reaction for the synthesis of ethyl ethanoate from ethane is:

2 \mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}(\mathrm{~g})+2 \mathrm{HCl}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

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(i)

The progress of the reaction was followed until equilibrium was reached.

Sketch a graph showing how the rates of the forward and reverse reactions change from the beginning of the reaction, until equilibrium has been reached.

Figure for Question (i) — IB Chemistry HL

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(b)

Suggest a reason for the difference between the value of the equilibrium constant, K, determined from experimental values in (e)(i) and the correct value calculated for K, in (d)(viii).

If you did not obtain values for these, use 7.15 for (d)(viii) and 3.75 for (e)(i), although these are not the correct values.

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IB Chemistry HL 2.3.1 Dynamic Equilibrium Questions question 1

Question (a)

Question (i)

Question (b)