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Physics > Chemical Equilibrium and Rates Of Reaction > Flashcards

Chemical Equilibrium and Rates Of Reaction Flashcards

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1
Q

Dynamic Equilibrium

A

Two reversible processes are occurring simultaneously at the same rate

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2
Q

Open System

A

One in which both energy and matter can be exchanged between the system and its surroundings

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3
Q

Closed System

A

One in which both energy and matter can be exchanged between the system and its surroundings

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4
Q

Dynamic chemical equilibrium

A

In a closed system, the rate if the forward reaction is equal to the rate of the reverse reaction

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5
Q

Common ion effect

A

When an ion is common in both reactions and increasing concentration of a substance disturbs equilibrium. Where there is more ions, that reac will be favoured.

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6
Q

yield

A

A measure of the amount of product obtained in a chem reaction compared to the amount of product that is possible

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7
Q

Equilibrium constant

A

-A number that shows to what extent the reactants have changed into products by the time equilibrium is established.
-Affected only by temperature

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8
Q

Equilibrium constant

A

Kc= [p] / [r]
High: pr

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9
Q

Heat of a reaction

A

The net change of chemical potential energy of the system

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10
Q

Exothermic reactions

A

Reactions which transform chemical potential energy into thermal energy
Bond formation: the stronger the bond the more energy is released when formed

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11
Q

Endothermic reactions

A

Reactions which transform chemical potential energy into chemical potential energy
Bond breaking: the stronger the bond the more energy it requires to break

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12
Q

Activation energy

A

The energy required to form the activated complex

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13
Q

Activated complex

A

A high energy, unstable, temporary transition state between reactants and the products

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14
Q

Reaction rate

A

The change in concentration per unit time of either a reactant or product

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15
Q

Average vs Instantaneous reaction rates

A

The average rate=change in concentration over a period of time. It depends on when you take the measurements. The instantaneous rate is the rate at a particular time. It is determined by finding the slope of the tangent to the concentration vs time curve at that time.

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16
Q

Factors that affect rate of chem reactions

A
  1. Nature of substances that react
  2. Surface Area of a solid
  3. Concentration of a solution
  4. Pressure of a gas
  5. Temperature
  6. Catalyst
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17
Q

Catalyst

A

A substance that increases the rate of the reaction but remains unchanged at the end of the reaction

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18
Q

Collision Theory

A

A model that explains that a reaction will only proceed when the reactant particles collide effectively. An effective collision occurs when there’s:
1. Correct Orientation:
2. Sufficient Energy: Ek>=Ea
*apply to various factor

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19
Q

Explain how the Nature of reacting substances affect rate of reaction?

A
  1. Gas tends to react faster than other natures of substances
  2. Simple aqueous ions tend ti react almost instantly
  3. Reactions involving ions tend to be faster than reactions involving molecules
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20
Q

Explain in terms of coll theory how surface area of solid affects rate of reaction?

A

Concept: Reactions occur on the outer layer of solids

=Surface area increases the number of coll per between reactant particles will increase
:. The no, of successful coll per unit time will increase
:. Increasing ror
This is because more particles of solid are exposed to other reactant

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21
Q

Explain in terms of coll theory how pressure of gas will affect ror?

A

GASES ONLY
Increasing the pressure brings particles closer together
:. Increasing the no. Of coll per unit time
:. Increase in successful coll per unit time
:. Increasing ror

22
Q

Explain in terms of coll theory how temperature will affect ror?

A

temp dp Ror:
Increasing temperature increases the kinetic energy of the particles
:. More particles will have energy => Ea
:. The particles will collide more frequently
This increase the no. Of successful coll per unit time
:. Increasing reaction rate

23
Q

Explain in terms or coll theory how will catalyst affect ror?

A

Catalyst lowers activation energy of a reaction.
:. A lower Ea means more particles will have enough to react
There will be more coll:. More successful coll per unit time
Increasing ror

24
Q

Explain in terms of coll theory the relationship between reaction rate and the number of eff unit coll per u time.

A

Directly proportional:

25
Q

Measuring Rates of Reactions: Suggest and explain each

A

Measuring of gas volumes:
Gas formed: Measure volume of gas-use syringe, use water to count bubbles
Precipitate: Measure turbidity per unit time of the reaction mixture
Colour change: measure time taken for colour change.

26
Q

Graphs

A
  1. Maxwell Boltzmann
  2. Potential Energy Profile/ Enthalpy
  3. Conc v time
  4. Vol v time
  5. Ror v time (“normal”)
  6. No. Of particles v time
27
Q

Reversible reaction

A

One in which products can be converted to reactants

28
Q

Le Chat

A

When an external stress (change in pressure, temperature or concentration) is applied to a system in dynamic chemical equilibrium, the equilibrium point will change in such a way as to counteract that stress

29
Q

Explain in terms of the rates of forward and reverse reactions the effect of the changes of pressure, temperature and concentration on the concentration/s and/or amounts of each substance in an equilibrium mixture

A
  1. Pressure
  2. Temperature
  3. Concentration
30
Q

Graphs for chem reactions

A

Amount (no. Of moles) v time:
Concentration v time
Rate v time

31
Q

Industrial processes: Chem equations, diagrams or flowcharts

A

Apply rate and equilibrium principles to describe how yield is affected in various industrial processes
In industrial processes conditions are chosen for their economic viability to prioritise over yield. Hence a process that has a high rate is more economically viable than a process with high yield.

32
Q

Equilibrium Constant: explaination

A

the ratio of the equilibrium concentrations of products over the reactants each raised to the power of their stoichiometric coefficients= concentrations of a reactants and products including their stoichiometry

33
Q

Industrial Process: Haber Process
F/R
Pressure
Temp
Catalyst

A

Endo <> Exo
Pressure: Mod-High (25-250atm)
Temp: Mod-High (400-450°C)
Catalyst: Iron Oxide

34
Q

Industrial Process: Contact Process

A

Endo<>Exo
Pressure: Low (1-2atm)
Temp: Mod-High (400-450°C)
Catalyst: Vanadium Pentoxide V205

35
Q

Industrial Process: Otswald Process

A

Endo<>Exo
Pressure: Low-Mod (4-10atm)
Temp: High (900°C)
Catalyst: Platinum/Rhodium

36
Q

Explain in terms of coll theory how concentration affects rate of reaction?

A

Concentration of reactants is dp to ror:
Increasing concentration will increase the no. of particles per unit volume
This will increase the no. of coll per unit time
:. Increase the no. Of successful coll per unit time

37
Q

Concentration of reactants: How to change concentration

A

No solids or pure liquids
Aqueous solution: Adding more solute
Gas: Adding more gas, increasing pressure

38
Q

Graph question (pg13) label A,B,C,D

A

Answers on page

39
Q

Graphs: Use of Maxwell-Boltzmann Distribution

A

Shows the distribution of kinetic energies
Area under graph=measure of total particles present
Increasing temperature: Ea stays the same, Graphs stretches (more particles + woder spread of mean energy)

40
Q

KC constant

A

Written out with letters as equilibrium expression
Coefficients become exponents

41
Q

Dynamic equilibrium graphs

A

The reaction rate versus time graph looks like a wine glass tipped on its side with the forward reaction on top and the reverse reaction at the bottom meeting way equilibrium is reached

The concentration versus time graph looks like half of a fish with his tail and body. With the reactants starting at the top and the product starting off at the bottom as constant concentrations are constant

42
Q

What is the effect of catalysts

A

Catalyst increase the rate of the forward and reverse reaction equally
Catalyst only cause a reaction to reach equilibrium faster
Catalyst therefore have no affect on the position of the equilibrium

43
Q

The harbour process

A

It is the combination of nitrogen and hydrogen to make ammonia
XO thermic forward reaction
Endothermic reverse reaction
Moderate to high pressure 25-250
Moderate to high temperature 400 to 450
Iron oxide catalyst

44
Q

The contact process this is the manufacturing of sulphuric acid

A

The forward reaction is exothermic
Reverse reaction is endothermic
The pressure is love from 1 to 2
The temperature is moderate to high of 450 to 400
The catalyst is vanadium Penta oxide which is V205

45
Q

The Ostwald process

A

manufacturing of nitric acid
The forward reaction is exothermic
The reverse reaction is endothermic
The pressure is low to moderate from 4 to 10
The temperature is high 900
The catalyst is platinum or rhodium

46
Q

Energy profile exothermic

A

The energy of the products is less than the energy of the reactants in order to read XS energy

47
Q

Energy profile endothermic

A

The energy of the products. More than the reactants as they need energy that is not sufficient in the reactants and therefore they take energy from the products

48
Q

How do you measure the rate of the reaction when a gas is formed

A

If a gas is produced we can measure the volume of the gas produced using a gas syringe in a Sealed container with a cork, are use water to count the bubbles
A gas can be allowed to escape and we can measure the change in mass per unit time of the reaction mixture

49
Q

Measuring the rate of reaction is when a precipitate forms

A

If a precipitate is formed we can measure the turbidity (the degree of cleaners) per unit time of a reaction mixture
This would be done by drawing an X at the bottom of the container and sing up until what time point the ex is no longer visible

50
Q

Measuring the rate of reactions with the colour change

A

If a colour changes observed we can measure the time taken for the colour change to Occur 

51
Q

What are different ways one can measure the rate of reaction is

A

Measuring the Change in the Number of moles or product per unit time
The change in concentration of reactant our product per unit time
Change in the mass of reactant our product per unit time
Change in volume per unit time

52
Q

Factors that affect rate of reactions

A

Nate of reactant
Concentration of reactant
Temperature of reactant
Surface area of solid
Pressure of reactant
Use of a catalyst

Physics (14 decks)

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