Chemical equilibrium — Question 25

25a)

The reaction occurred in a closed system, therefore matter is not exchanged with the surroundings. This means the system can reach a steady state, where the rate of the forward reaction (conversion of reactants to products) equals the rate of the reverse reaction (products are converted back into reactants) to establish a state of dynamic equilibrium.

• identifies gases reach dynamic equilibrium [1 mark]

• explains matter is not exchanged with surrounds [1 mark]

• explains rate of forward reaction is equal to rate of reverse reaction [1 mark]

25b)

$•\,\mathrm{d}\mathrm{e}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{s}\,\mathrm{K}_{\mathrm{c}}\,=\,0.25\,[1\,\mathrm{m}\mathrm{a}\mathrm{r}\mathrm{k}]\,$

$•\,\mathrm{i}\mathrm{n}\mathrm{d}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{s}\,\mathrm{t}\mathrm{h}\mathrm{a}\mathrm{t}\,\mathrm{s}\mathrm{i}\mathrm{n}\mathrm{c}\mathrm{e}\,\mathrm{K}_{\mathrm{c}}\,<\,1,\,\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{b}\mathrm{r}\mathrm{i}\mathrm{u}\mathrm{m}\,\mathrm{l}\mathrm{i}\mathrm{e}\mathrm{s}\,\mathrm{t}\mathrm{o}\mathrm{w}\mathrm{a}\mathrm{r}\mathrm{d}\mathrm{s}\,\mathrm{t}\mathrm{h}\mathrm{e}\,$

$\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{s}\,[1\,\mathrm{m}\mathrm{a}\mathrm{r}\mathrm{k}]\,$