pk 2 chem 2 - Chapter 14 Chemical Equalibrium Reversible...

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Chapter 14 Chemical Equalibrium
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Reversible Reactions In the above reaction H 2 and I 2 react to form 2 HI molecules. However, the 2 HI molecules can also react to reform the H 2 and I 2. A reaction that can proceed in both the forward and reverse direction is called Reversible. When the forward reaction has a rate equal to the rate of the reverse reaction the H 2 (g) + I 2 (g) 2 HI (g)
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Hypothetical Reaction 2 Red Blue Concentration vs. Time for 2 Red --> Blue 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0 20 40 60 80 100 120 140 Time, sec Concentration [Red] [Blue]
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H 2 ( g ) + I 2 ( g ) 2 HI( g ) at time 0, there are only reactants in the mixture, so only the forward reaction can take place [H 2 ] = 8, [I 2 ] = 8, [HI] = 0 at time 16, there are both reactants and products in the mixture, so both the forward reaction and reverse reaction can take place [H 2 ] = 6, [I 2 ] = 6, [HI] = 4
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H 2 ( g ) + I 2 ( g ) 2 HI( g ) at time 32, there are now more products than reactants in the mixture the forward reaction has slowed down as the reactants run out, and the reverse reaction accelerated [H 2 ] = 4, [I 2 ] = 4, [HI] = 8 at time 48, the amounts of products and reactants in the mixture haven’t changed – the forward and reverse reactions are proceeding at the same rate – it has reached equilibrium
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H 2 ( g ) + I 2 ( g ) 2 HI( g ) Concentration Time Equilibrium Established Since the [HI] at equilibrium is larger than the [H 2 ] or [I 2 ], we say the position of equilibrium favors products As the reaction proceeds, the [H 2 ] and [I 2 ] decrease and the [HI] increases Since the reactant concentrations are decreasing, the forward reaction rate slows down And since the product concentration is increasing, the reverse reaction rate speeds up Once equilibrium is established, the concentrations no longer change At equilibrium, the forward reaction rate is the same as the reverse reaction rate
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pk 2 chem 2 - Chapter 14 Chemical Equalibrium Reversible...

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