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QUESTION 1 A partly filled water bottle is sealed and left on a bench in a room with a constant temperature. After several minutes it is noted that the water level in the bottle remains constant. In the water bottle the rate of evaporation 1s (A) less than the rate of condensation. (B) greater than the rate of condensation. (C) equal to the rate of condensation and equal to zero. (D) equal to the rate of condensation but not equal to zero
QUESTION 25 (5 marks) This graph depicts the changes in concentration over time for a nitrogen dioxide / dinitrogen tetroxide gaseous equilibrium in a closed system at constant temperature. 0.120 0.100 fl = 0.080 + je) ÔøΩ & ÔøΩ 0.060 E 3 0.040 = fe) Y 0.020 0 20 40 60 80 100 120 140 160 180 200 220 Time (s) a) Determine the balanced chemical equation for the reaction in this system. [1 mark] b) Identify the time at which equilibrium is reached. [1 mark] c) Iftemperature is held constant predict the effect that doubling the volume at 100 seconds would have on the closed system by sketching the change that would occur and the approximate position of the new equilibrium on the graph. [3 marks] Note: If you make a mistake draw a line through this graph and use the additional graph provided on page 13 of this question and response book
QUESTION 1 Melting is a (A) physical change that is reversible. (B) chemical change that is reversible. (C) physical change that is irreversible. (D) chemical change that is irreversible
QUESTION 25 (5 marks) An equilibrium is formed between two differently coloured cobalt species Co(H 0) 2 * (aq) which is pink and CoCÔøΩ ~(aq) which is blue. The equation for this equilibrium is shown. a) b) Co(H 0) * (aq) + 4CI (aq) = CoC ÔøΩ (aq) + 6H 0(1) Apply Le ChatelierÔøΩs principle to predict the visible epee of adding AgNO; to an aqueous blue-coloured solution containing Co(H 0) 7* and CoClyÔøΩ ions. Explain your reasoning. When a sample of the equilibrium mixture is put into hot water the mixture turns more blue. Determine whether the forward reaction of the equation is exothermic or endothermic. Explain your reasoning. [3 marks] [2 marks]
QUESTION 26 (5 marks) The graph represents changes in concentration over time for three gaseous molecules (X Y and XY) in a closed system at constant temperature and pressure. X +Y = 2XY Concentration (mol L) Time a) Identify whether XY is the reactant or the product. [1 mark] b) Calculate the equilibrium constant (K ) value. [2 marks] (to two significant figures) c) Determine whether the position of equilibrium favours the reactants or products. Explain your reasoning. [2 marks]
QUESTION 25 (5 marks) Three unknown gases are combined in a sealed flask and allowed to reach equilibrium as shown by the equation. 3A (g)+X(g) = 2XA;3(g) a) Determine whether the gases reach a state of dynamic equilibrium. Explain your reasoning. [3 marks] b) Determine if the relative position of equilibrium lies towards the products or reactants if the molar concentrations at equilibrium are 3.4 mol L! for A> 1.8 mol L! for X> and 4.2 mol L! for XA. Explain your reasoning. [2 marks]
QUESTION 7 (4 marks) When heated in a sealed container solid mercury(II) oxide (HgO) decomposed to form metallic mercury (Hg) and oxygen gas (O ). 2HgO(s) = 2Hg(l) + 0 (g) Orange Silver Colourless (a) Identify whether the reaction occurs in an open or closed system. [1 mark] (b) Explain why the colour of the system does not change once equilibrium is established. [3 marks]
QUESTION 1 In a chemical equation at equilibrium a reversible arrow (=) symbolises that (A) the forward reaction has stopped but can be reversed. (B) the moles of reactants and products present are equal. (C) half of the reactants have been converted into products. (D) the concentration of reactants and products remains constant.
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