(b) Controlling the rate Flashcards

1
Q

What is the rate of reaction?

A

The speed at which the reaction occurs.

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2
Q

What must happen for a reaction to occur?

A

Reactant particles must collide with sufficient kinetic energy, it must be greater than the activation energy.
And have the correct collision geometry.

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3
Q

What is the formula to work out average rate of reaction?

A

Change in quantity/ change in time.

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4
Q

What are the 2 ways to collect and measure gas?

A

Use a gas syringe and downwards displacement through water.

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5
Q

What is a way which you can measure the course of a reaction?

A

Measuring the change in mass.

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6
Q

What are the 4 factors affecting rate of reaction?

A

Temperature
Concentration
Particle size
Use of a catalyst.

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7
Q

What is the activation energy?

A

The minimum energy required by colliding particles to produce an activated complex.

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8
Q

What does increasing the concentration do to the rate of reaction?

A

Increases it.

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9
Q

Why does increasing the concentration increase the rate of reaction?

A

There are more particles in the same space, this means more collisions are likely. When particles collide with sufficient energy a reaction will occur.

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10
Q

How does particle size affect the rate of reaction?

A

A bigger particle size means that there is less surface area and so less collisions occur. A smaller particle size increases the amount of surfaces and so more collisions occur.

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11
Q

What is an activated complex?

A

An activated complex is an unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction.

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12
Q

In an exothermic reaction what happens?

A

Energy, in the form of heat, is given out.

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13
Q

What is the energy relationship between the products and reactants in an exothermic reaction?

A

The products have less energy than the reactants.

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14
Q

What is the delta H always in an exothermic reaction?

A

Negative.

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15
Q

Describe a potential energy diagram for an exothermic reaction.

A

It will go along, up and then down and along, and the second line will be lower than the first.

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16
Q

What is an exothermic reaction?

A

One in which energy is absorbed from the surroundings.

17
Q

What is the delta H always in an exothermic reaction?

A

Positive.

18
Q

Describe the potential energy diagram of an endothermic reaction.

A

It will go along, up, down, and along. The second line will be higher up than the first.

19
Q

What does a distribution curve show?

A

The amount of reactions that result in a reaction, OR the amount of collisions that collide with the sufficient activation energy.

20
Q

What is a catalyst?

A

A catalyst provides an alternative route which involves less energy and so lowers the activation energy.

21
Q

What is a homogeneous catalyst?

A

A catalyst which is in the same state as the reactants.

22
Q

What is a heterogeneous catalyst?

A

A catalyst which is in a different physical state to the reactants.

23
Q

Does a catalyst affect the delta H value?

A

No.

24
Q

What are the 3 stages in a reaction with a catalyst?

A

Adsorption, Reaction, Desorption.

25
Q

What is the delta H value?

A

The difference in energy between the reactants and the products.

26
Q

How does pressure affect the rate of reaction?

A

The higher the pressure, the less space there is and so the likelihood of collisions is increased and so the reaction rate is increased.

27
Q

How does temperature affect the rate of reaction?

A

An increase in temperature increases the genetic energy of the reactants, meaning they move faster, this means that they are more likely to collide thus increasing the rate of reaction.

28
Q

How much do you need to increase the temperature to see a large increase in the rate of reaction?

A

If you increase by only 10 degrees it will almost double the rate.

29
Q

What is temperature a measure of?

A

Temperature is a measure of the average kinetic energy of the particles in a substance.