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Chemistry AS Unit 2 > Kinetics > Flashcards

Kinetics Flashcards

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1
Q

3 reasons for knowledge of rates of reactions

A

Can sped up or slow down a reaction in the laboratory
Can choose optimum conditions for reaction
Gives us information on how a reaction takes place

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2
Q

What are the five main factor that affect how fast a chemical reaction takes place?

A

Temperature, concentration, pressure, surface area and catalysts

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3
Q

Do the factors affecting the rate of chemical reaction affect the number or collisions involving reacting particles or activation energy?

A 
Temperature both
Concentration collisions
Pressure collisions
Surface area collisions
Catalyst both
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4
Q

What are the two things particles need to react?

A

Activation energy

Correct orientation

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5
Q

What is the difference between a homogeneous and heterogeneous reaction?

A

Homogeneous- reactants are in the same phase

Heterogeneous- reactants are in different phases

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6
Q

What is the definition of a catalyst?

A

A substance that changes the rate of a chemical reaction without being used up or undergoing any permanent chemical change

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7
Q

why are catalysts so useful in the chemical industry?

A

Enable a profitable reaction without resorting to excessive and expensive conditions of temperature and pressure

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8
Q

What does the rate of reaction describe?

A

The rate at which the reactants are used up and the products formed

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9
Q

What is the equation for calculating the rate of reaction?

A

Change in x/ time

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10
Q

Why is it more accurate to comparing Initial rate of reaction when comparing rates?

A

Because the rate changes as the reaction proceeds along with the amounts of reactants

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11
Q

What are two ways of monitoring the rate of reaction when a gas is given off?

A

Record the change in mass of the mixture

Record the volume of carbon dioxide gas given off

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12
Q

Why does starch turn blue black in the presence of iodine?

A

It forms a complex

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13
Q

When doing titrimetric analysis:
What is an aliquot?
What is quenching?
Why is the mixture quenched?

A

A small portion of the reaction mixture
Stopping the reaction
To prevent the reaction going any further until analysis can be carried out

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14
Q

What is the name of the equipment that can quantitively measure the colour change during a reaction?

A

Photoelectric colorimeter

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15
Q

What needs to happen to allow conductimetric Analysis to be carried out?

A

A change in the number of ions present

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16
Q

What does the rate of reaction measure in terms of collisions?

A

How frequently effective collisions occur

17
Q

What is the definition of activation energy? What is the symbol?

A

The minimum amount of energy required to start a reaction by breaking bonds
Ea

18
Q

What causes particles without activation energy to simply bounce off each other?

A

The repulsion between their negative electrons clouds

19
Q

What happens during an unsuccessful collision between reactant particles?

A

Particles move towards each other, slow down, stop, then fly apart again unchanged

20
Q

What happens to the kinetic energy of particles as they come together?

A

It goes down and is transformed into potential energy

21
Q

What happens on exothermic reaction profile?

A

Ea- reactant molecules are coming together and bonds are breaking apart. Energy is being absorbed
Product molecules are forming and moving away from each other. Energy is being released

22
Q

What property of the reacting particles determines whether the activation energy will be met or not?

A

The combined initial kinetic energies of the colliding particles

23
Q

What happens during a reaction with a catalyst?

A

Particles come together and bonds start to break
Activated complex forms
Activated complex bonds break
Product molecules form and move apart

24
Q

What is the definition of an activated complex?

A

A transitional structure in a chemical reaction that results from an effective collisions between molecules and that persists while old bonds are breaking in new bonds are forming

25
Q

Do you all particles in a reaction mixture have the same amount of chemical energy?

A

No

26
Q

What is the Mazwell-Boltzmann model?

A

A model for expressing the distribution of energy among the molecules of a gas in thermal equilibrium

27
Q

What does the area under a graph in a Maxwell Boltzmann model represent?

A

The total number of particles

28
Q

What does the peak on a Maxwell Boltzmann model represent?

A

The average speed of the particles

29
Q

How does a catalyst speed up the reaction?

A

Catalyst provides an alternative route/mechanism (1)
with lower activation energy
ALLOW low activation energy (1)
So a higher proportion (ALLOW more) molecules / collisions (ALLOW reactants) have energy equal to or greater than Ea

Chemistry AS Unit 2 (13 decks)

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