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Hydrogen iodide dissociates into its elements according to the following equation - VCE - SSCE Chemistry - Question 8 - 2008 - Paper 1
Question 8
Hydrogen iodide dissociates into its elements according to the following equation. $$2HI(g) \rightleftharpoons H_2(g) + I_2(g)$$ \(\Delta H = +9 \text{ kJ mol}^{-1... show full transcript
Worked Solution & Example Answer:Hydrogen iodide dissociates into its elements according to the following equation - VCE - SSCE Chemistry - Question 8 - 2008 - Paper 1
Step 1
Effect of Decreased Volume on Equilibrium Concentration
Answer
When the volume of a gaseous mixture is decreased, the pressure of the system increases. According to Le Chatelier's principle, the equilibrium will shift in the direction that produces fewer moles of gas to counteract the change in conditions. In this reaction, 2 moles of (HI(g)) yield 1 mole of (H_2(g)) and 1 mole of (I_2(g)), resulting in a total of 2 moles of reactants converting to 2 moles of products. Therefore, upon decreasing the volume to 1.3 L, the equilibrium will shift towards the production of more (H_2(g)) and (I_2(g)) as it seeks to relieve the pressure increase.
The graph that best represents this scenario would show an immediate decrease in the concentration of (HI(g)) as it dissociates into (H_2(g)) and (I_2(g)), followed by a gradual leveling off as the system reaches a new equilibrium.
Step 2