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12 Cards in this Set
- Front
- Back
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What is the definition of a dynamic equilibrium?
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It is an equilibrium where the rate of the forward reaction equals the rate of the backwards reaction.
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How would you write a Kc expression?
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Kc=products/reactants
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Write a Kc expression for H2g + I2g <-> 2HIg.
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Kc=[HIg]2/[H2g][I2g]
the [HIg] is squared because there are 2 moles of it. |
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When would you use a Kp expression?
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For a reaction when the reactants and products are in units of pressure, i.e gasses in Pa or atmospheres.
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Write a Kp expression for H2g + I2g <-> 2HIg.
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Kp=P2HIg/PH2g PI2g
In the P2HIg the 2 should be a superscript squared sign due to the fact that there is 2 moles of HI. |
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What dpes the Kc value tell us about the position of the equilibrium?
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If Kc>1 then the products predominate and therefore the equilibrium is said to lie to the right. If Kc<1 then the reactants predominate and the equilibrium lies to the left.
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What effect will changing the temperature have on the value of Kc in an exothermic reaction.
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If the temp. increases the reaction will move to the left and thereforethe Kc value will decrease. If the temp. decreases the reaction will move right and therefore the Kc will increase.
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What effect will changing the temp. have on the Kc value in an endothermic reaction.
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Increasing the temp. will push the reaction right and increase the Kc value. Decreasing the temp. will push the equilibrium left and therefore decrease the Kc value.
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If you have the Kc of the forward reaction, how would you find the Kc of the backwards reaction from that Kc value.
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1/Kc
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What does the ΔG value tell us about the Kc value?
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If ΔG is negative then it means that the products predominate and so there is a large Kc value. Conversely if ΔG is positive then the reactants predominate and the Kc value will be small.
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What is the difference in what can be deduced from kinetic and equilibrium data?
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Kinetic data tells us how fast a reaction goes.
Equilibrium data tells us how far a reaction goes. |
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How can equilibrium data be interpreted and used in industry? e.g with the Haber process.
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With N2g + 3H2g <-> 2NH3g ΔH=-92.4 kJmol-1 according to Le Chatelier's principle and increase in pressure will favour the side with the fewer moles (the NH3). An increase in temp. would favour the reactants due to the reaction being exothermic. So although low temp. increases the yield of NH3 it also means that equilibrium is reached too slowly. An optimum temp of around 400-450oC with an iron catalyst is used.
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