This page contains the AQA AS Chemistry C6 Equilibria Questions and their Kerboodle answers for revision and understanding Equilibria.This page also contains the link to the notes and video for the revision of this topic.
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6.1 The idea of equilbrium AQA AS Chemistry C6 Eqilibria Kerboodle Answers: Page No.106
1.Ans-
- True
- False
- True
- False
2.Ans- When equilibrium is reached the rates of forward and backward reactions become equal.
6.2-Changing the conditions of an equilibrium reaction AQA AS Chemistry C6 Eqilibria Kerboodle Answers: Page No.108
1.Ans- Only reaction (a) will be affected by as the number of gaseous molecules are different on both the sides.
2.Ans-
- It will move to left
- No change
- It will only decrease the activation energy of the reactions as it paves an alternative path for the reaction to proceed.It will not affect the equilibrium position.
- High pressure is favourable for the maximum yield of ammonia
6.3- Equilibrium reactions in industry AQA AS Chemistry C6 Eqilibria Kerboodle Answers: Page No.111
- Ans- It is used in form of a fine gauze so as to increase the surface area of the catalyst and therefore its efficiency.
- Ans- Ethanol produced by fermentation is a renewable resource while ethanol made by the hydration of ethene is a non-renewable fuel. This is because ethene is produced by cracking crude oil fractions, and crude oil itself is a non-renewable resource.
- Ans- Yes because synthesis gas can be produced from something that is or was ever a plant.
6.4-The Equilibrium constant Kc AQA AS Chemistry C6 Eqilibria Kerboodle Answers: Page No.114
1.Ans-
- Kc=[C]/[A][B]
- Kc=[C]/[A]2[B]
- Kc=[C]2/[A]2[B]2
- Ans-
- Unit= mol-1 dm3
- Unit=mol-2 dm6
- Unit=mol-2 dm6
3.Ans-
- Kc=[0.117][0.117]/[0.083][0.083]=1.987
- This is because the total number of molecules are same on the reactants and the products side and hence the volume cancels each other.
- It is to the left as the concentration of products in the above case was=2/3
6.6- The effect of changing conditions on equilibria AQA AS Chemistry C6 Eqilibria Kerboodle Answers: Page No.119
- Ans-
- It will increase
- No change as the reaction will move forward and balance this increment.
- No change.
- Ans- Yes this suggestion is sensible because this would lead to decrease in the concentration of one of the products i.e water and hence according to Le Chatlier’s principle the reaction would move in forward direction to counter this effect hence the yield of ethyl ethanoate would increase.
- Ans-
- Increases
- Does not change
- Decreases
- Does not change
- Does not change
Practice Questions:
1.Ans-
- A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change.At this stage the forward and backward reaction do not come to a halt but they continue at a same rate.
- High yield of methanol is favoured by high pressure because the number of molecules of gaseous products are less on the reactant side and according to Le Chatlier’s principle the reaction moves in the direction with lesser number of molecules when the pressure is increased so as to counter its effect.
- This is because the cost of building such high pressure resistant systems is expensive and producing higher pressure is also very expensive.
- On increasing the temperature the reaction will move to left as the forward reaction is exothermic in nature so the yield of methanol will decrease.
- An increased temperature is required due to increased activation energy the presence of catalyst decreases the activation energy as it paves an alternative path for reaction to proceed.
2.Ans-
- Oxidation in terms of electrons can be defined as the process of loss of electrons.
- On increasing the temperature the reaction would proceed in forward direction as per Le Chatlier’s principle to counter the changed conditions hence the yield of nitrogen monoxide will increase.But on increasing the pressure,the yield will not be affected as the number of gaseous molecules are same on both the sides.
3.Ans-
- It states that if a system at equilibrium is disturbed,the equilibrium moves in the direction that tends to reduce the disturbance.
- i) The yield of hydrogen will decrease as on increasing the pressure the number of molecules in a given volume increases and therefore to counter this the reaction will move in a direction of less gaseous molecules i.e towards the left.
- ii) The yield of hydrogen will increase as the reaction will move in forward direction to counter the increased concentration of a reactant.
- Higher temperatures than this are not used because it has high maintenance costs besides building such plants are very expensive.
4.Ans-
- Src-http://i.imgur.com/6ZWW8U7.jpg
- It states that if a system at equilibrium is disturbed,the equilibrium moves in the direction that tends to reduce the disturbance.
- Curve B because the value of Kc is same for both the experiments.The shape is different due to pressure differences as high pressure will increase the yield of ammonia hence the number of moles.
- Curve C,because the concentration of ammonia is same at equilibrium which means Kc is same for both of the reactions. This is because due to catalyst the equilibrium is attained far more quickly.
5.Ans-
- i) Kc=[0.25]4[0.15] / [0.48]2[0.10] ii)0.02543 mol2 dm-6
- Increase in volume means decrease in pressure so the reaction will move in forward direction and therefore the concentration of hydrogen will increase.
- This is because on decreasing the temperature the reaction moves in backward direction as per Le Chatlier’s principle to counter the changed conditions and therefore will lead to a decreased amount of hydrogen.