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CHEMISTRY as - ocr a > 10- Reaction Rates And Equilibrium > Flashcards

10- Reaction Rates And Equilibrium Flashcards

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1
Q

Rate of a chemical reaction definition

A

Measures how fast the reactants are being used up or products are being formed

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2
Q

Rate of reaction (concentration) definition

A

The change in concentration of a reactant or product in a given time

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3
Q

What conditions are required for a reaction to take place

A

The particles collide with the correct orientation

The particles must have sufficient energy to overcome the activation energy barrier of the reaction

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4
Q

Activation energy definition

A

The minimum amount of kinetic energy required for a reaction to occur

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5
Q

What 5 things can alter the rate of a chemical equation

A

Increasing temperature

Increasing SA

Increasing pressure

Increasing concentration

Use of a catalyst

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6
Q

How does temperature affect the rate of reaction

A

Temperature increases the rate of reaction by…

Increases KE of particles

Greater proportion of the particles will have at least the activation energy - more effective collisions

Causes them to move faster and collide more frequently increasing the chances of effective collisions

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7
Q

How does concentration / pressure alter rate of a chemical reaction

A

Increasing concentration/pressure increases the rate of reaction

It increases the number of particles in the same volume

Particles are closer together

Collide more frequently

More likely to be more effective collisions

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8
Q

How do catalysts affect rate of reaction

A

Catalysts increase rate of reaction

They lower the activation energy

By providing an alternative reaction pathway

A greater proportion of particles will have enough energy to react

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9
Q

What are the different types of ways to measure reaction rates

A

How quickly the reactants are used up = removal of reactant

How quickly the products are formed = formation of a product

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10
Q

List of ways of measure rate of reaction practicals

Record then graph …

A
  • colour changes in solutions
  • mass change
  • volume of gas produced
  • pressure changes in gasses
  • changes in conductivity
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11
Q

Monitoring the loss of mass of reactants using a balance practical

A

1) add reactants to conical flask
2) record initial mass
3) add catalyst
4) record mass at regular intervals until no change

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12
Q

Monitoring volume of gas produced at regular time intervals using gas collection

A

1) add reactants to conical flask and replace bung
2) record the initial volume
3) add catalyst
4) measure volume at regular interval changes

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13
Q

Catalyst definition

A

A catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged by the end of the reaction

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14
Q

Heterogeneous catalyst definition

A

A reaction in which the catalyst has a different physical state from the reactants

Reactants = gases
Catalyst = solid
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15
Q

How does a heterogenous catalyst operate

A

Reaction takes place on surface of the catalyst
Reactant is absorbed onto surface (forms weak bonds)
Product leaves through desorption

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16
Q

Homogenous catalyst definition

A

A reaction in which the catalyst and the reactants are in the same physical state

Aqueous

17
Q

How do homogeneous catalysts operate

A

Catalysts react with the reactants to form an intermediate species

Which breaks down to give products and regenerates the catalyst

18
Q

What is the economic importance of catalysts

A
  • Catalysts lower the production costs
    By producing more products in shorter time
    And reducing the energy required by using lower temperatures
  • change the properties of a product to make it more useful
19
Q

Why are catalysts good for environmental sustainability

A

-Preserves energy

-Reduces waste
By producing fewer pollutants as higher at economy
Convert harmful pollutants into safer ones

20
Q

What is Boltzmann distribution

A

The spread of molecular energies in gases

21
Q

What does Boltzmann distribution curve show

A

Shows the different kinetic energies a number of molecules have in a substance

22
Q

How does increasing temperature affect a Boltzmann distribution curve

A

Temperature increases the average energy of the molecules - molecules have higher energy

The graph will stretch

  • the peak will be lower
  • and further along the x axis
  • area is the same
23
Q

How do catalysts affect the Boltzmann distribution curve

A

Activation energy is lower on graph

More particles in effective collisions area

24
Q

Dynamic equilibrium definition

A

The equilibrium that exists in a closed system when the rate of the froward reaction is equal to the rate of the reverse reaction and concentration do not change

25
Q

Reverse reaction definition

A

A reaction that takes place in both the forward and reverse direction

26
Q

Homogenous equilibrium definition

A

Equilibrium in which all of the reactants and products are present in a single solution (in the same phase)

27
Q

What 3 things can change the position of equilibrium

A

Concentration
Pressure
Temperature

28
Q

Le chapeliers principle

When a system in dynamic equilibrium is subjected to a external change, the system readjusts itself to…

A

minimise the effect of the change and restore equilibrium

29
Q

Concentration rules
Le chateliers principle

When concentration of reactants increases

A

Shift to the side to get rid of that reactant

Minimise the extra reactant

30
Q

When pressure increases

Chateliers principle

A

Shifts to the side with the fewest molecules

To minimise the increase in pressure

31
Q

When temperature increases

Le chateliers principle

A

Shifts to endothermic direction
That absorbs this heat
To minimise the increases in temp

32
Q

Catalyst effect on position of equilibrium

A

Has no effect
Just speeds up the rate of forwards and reverse reactions equally
Equilibrium reached faster

33
Q

Why compromise temp in industries

A

Although low temp produces higher yield

The rate of reaction is too slow

So compromise between yield and faster reaction

34
Q

Why compromise pressure

A

High pressure produces higher yield and rate of reaction

But is expensive and unsafe

Compromise between yield and expense

35
Q

Equilibrium constant

A

Gives you an idea of how far to the left or right the equilibrium is

36
Q

Kc = 1

Equilibrium =

A

Halfway between reactants and products

37
Q

Kc > 1

Equilibrium =

A

Towards the products

Further to the right

38
Q

Kc < 1

A

Towards the reactants

Further to the left

CHEMISTRY as - ocr a (15 decks)

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