Unit 1: Section 5- Kinetics + RP3 Flashcards

1
Q

What is dynamic equilibrium?

A

The rates of the forwards and backwards reaction are the same, the concentrations of the products and reactants are constant.

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2
Q

What is Le Châtelier’s Principle?

A

Equilibria will change their position to counteract any change in their conditions.

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3
Q

How does increasing pressure effect equilibrium?

A

If the pressure of a system is increased, the equilibrium opposes the change by shifting to the side which produces the fewest moles of gas to reduce the pressure.

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4
Q

How does decreasing pressure effect equilibrium?

A

If the pressure of a system is decreased, the equilibrium opposes the change by shifting to the side which produces the most moles of gas to increase the pressure.

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5
Q

How does increasing temperature effect equilibrium?

A

If the temperature of a system is increased, the equilibrium shifts in the endothermic direction to oppose the change and reduce the temperature by absorbing heat.

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6
Q

How does decreasing temperature effect equilibrium?

A

If the temperature of a system is decreased, the equilibrium shifts in the exothermic direction to oppose the change and increase the temperature by giving out heat.

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7
Q

How does increasing the concentration of something effect equilibrium?

A

The equilibrium system will shift in the direction that reduces the concentration of that species.

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8
Q

What happens if you change the pressure of a reaction where there are the same number of moles of gas on each side?

A

Changes in pressure will have no effect on the position of the equilibrium.

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9
Q

What effect do catalysts have on the position of equilibrium?

A

Catalysts do not affect the position of equilibrium as they speed up the rate of the reaction of both the forward and backward reaction by the same amount. Catalysts will however cause the system to reach equilibrium more quickly.

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10
Q

What is used in industry to maximise yield of chemical reactions?

A

Le Châtelier’s principle is used in industry to maximise yield

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11
Q

What is the contact process?

A

Stage 1: S(s) +O2(g)→SO2(g)

Stage 2: SO2(g) + 1/2 O2(g) ⇌SO3(g)

ΔH=−97 kJ mol −1 (dont need to know numbers)

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12
Q

What temperature is need for the contact process and why?

A

Stage 2 of the contact process is exothermic so a low temperature is needed to increase the yield. However, a low temperature would cause a slow rate so a compromise is made of 450°C

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13
Q

What pressure is needed for the contact process? (no numbers)

A

Having a high pressure would lead to high energy costs for marginal gains. This is because the effect of high pressure on yield is only slightly better.

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14
Q

What is the Haber process?

A

N2(g) +3H2(g) ⇌2NH3(g)

ΔH=−92kJ mol−1

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15
Q

What catalyst is used in the Haber process?

A

Iron

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16
Q

What temperature is needed for the Haber process and why?

A

The Haber Process is exothermic so a low temperature is needed to increase the yield. However, a low temperature would cause a slow rate so a compromise is made of 450℃.

17
Q

What pressure is needed for the Haber process?

A

Having a high pressure would lead to a higher yield as there are fewer moles of gas on the right. Therefore, high pressure is used. The pressure used is not too high because it would be expensive to maintain.

18
Q

What is the reaction for the hydration of ethene?

A

C2H4(g) + H2​O(g) ⇌ CH3CH2OH(l)

19
Q

What temperature is used for the hydration of ethene and why?

A

The hydration of ethene is exothermic so a low temperature is needed to increase the yield. However, a low temperature would cause a slow rate so a compromise is made of 300°C.

20
Q

What pressure is used for the hydration of ethene and why?

A

Having a high pressure would lead to a higher yield as there are fewer moles on the right so a high pressure is used. However, too high a pressure would lead to ethene being polymerised so a compromise of 60−70 atm is made.

21
Q

What is the reaction for the production of methanol?

A

CO (g) + 2H2(g) ⇌ CH3OH(g)

22
Q

What temperature is needed for the production of methanol?

A

The production of methanol is exothermic so a low temperature is needed to increase the yield. However, a low temperature would cause a slow rate so a compromise is made of 400°C.

23
Q

What pressure is needed for the production of methanol?

A

Having a high pressure would lead to a higher yield as there are fewer moles on the right so a high pressure is used. The pressure used is not too high because it would be expensive to maintain.

24
Q

What catalysts are used in the production of methanol?

A

Chromium and zinc oxides

25
Q

What is the equilibrium constant?

A

The equilibrium constant is a ratio that shows the relation between the concentration of products to the concentration of reactants.

26
Q

What does the higher the value of Kc mean?

A

the further to the right (i.e. towards the products) the equilibrium will lie

27
Q

What does the lower the value of Kc mean?

A

The further to the left (i.e. towards the reactants) the equilibrium will lie.

28
Q

How do you find Kc?

A

Divide the concentrations of the products by the concentration of the reactants.

29
Q

What is the only condition that effects Kc?

A

temperature

30
Q

What is the effect of an increased temperature on the Kc value of an exothermic forwards reaction?

A

The reaction will shift towards the reactants to oppose the increase in temperature. So, the equilibrium will shift to the left and the Kc value will decrease.