A closed gaseous system containing reactant X(g)X(g)X(g) and product Y(g)Y(g)Y(g) undergoes a reversible reaction to establish dynamic equilibrium. The variation in the rate of the forward reaction (RfR_fRf) and the rate of the reverse reaction (RrR_rRr) with time is shown in the graph below.
Which statement correctly describes the state of the chemical system at time t1 t_1\,t1 and time t2t_2t2?
At t1t_1t1, the reaction is in dynamic equilibrium because both the forward and reverse reactions are occurring simultaneously. At t2t_2t2, all chemical processes have stopped, meaning the concentrations of reactants and products remain constant.
At t1t_1t1, the rate of the forward reaction is greater than the rate of the reverse reaction, so the concentration of reactants is decreasing. At t2t_2t2, the rates of the forward and reverse reactions are equal and constant, so the concentrations of all species remain unchanged over time.
At t1t_1t1, the concentration of reactants equals the concentration of products because both curves are approaching each other. At t2t_2t2, the forward reaction rate is greater than the reverse reaction rate.
At t1t_1t1, the rate of the reverse reaction is greater than the forward reaction rate. At t2t_2t2, the system has reached a static state where the concentrations of reactants and products must be equal to each other.
Equilibria Questions
Practise OCR GCSE Chemistry Equilibria with exam-style questions for Foundation and Higher tier. 35 questions, matched to the OCR GCSE Chemistry (J248) specification and written in Paper 1 and Paper 2 (Foundation Tier) or Paper 3 and Paper 4 (Higher Tier) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.