The Rate and Extent of Chemical Change Flashcards

1
Q

How do you calculate mean rate of reaction?

A

Mean = Quantity of reactant used / time taken
OR
Mean = Quantity of product formed / time taken

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2
Q

What are the factors that affect the rate of chemical reactions?

A

Concentration
Presence of catalysts
Surface area of solid reactants
Pressure of gases
Temperature

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3
Q

What is temperature?

A

A measure if the average kinetic energy of its particles.

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4
Q

What is the pressure of a gas?

A

A measure of how much force it exerts on its container and on objects inside it.

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5
Q

What is a catalyst?

A

A substance that increases the rate of reaction but by the end of the reaction is unchanged chemically or in mass.

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6
Q

What needs to happen for a chemical reaction to occur?

A

Reactant particles need to collide with each other and the colliding particles need to have enough energy.

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7
Q

What is activation energy?

A

The minimum amount of energy that particles need for a reaction to happen.

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8
Q

Why is the rate of reaction greater if the reactant is powder than if it is a lump?

A

As the particle size decreases, the surface area to volume ratio increases. More of the reactant is exposed to particles of the other reactant. The energy of the particles doesn’t change the frequency of successful collisions increases.

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9
Q

How can you tell if a substance in a reaction mixture acts as a catalyst?

A

It is not shown in the chemical equation for the reaction by increases the rate of reaction.

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10
Q

Give an example of an enzyme used in chemistry.

A

Fermentation to make ethanol using enzymes in yeast.

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11
Q

If a reaction is endothermic in one direction, what is it in the other direction?

A

Exithermic

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12
Q

What does an increase in temperature cause?

A

An increase in the frequency of collisions and an increase in the energy of the particles.
A shift in the equilibrium position in the direction of the endothermic change.

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13
Q

What happens if you increase the pressure of a reacting gas in an equation?

A

The equilibrium position moves towards the side that has the smallest amount of gas molecules.

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14
Q

What effect on equilibrium position does an increase in concentration cause?

A

A shift away from the substance that is increased in concentration.

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15
Q

What effect does adding catalyst have on equilibrium position?

A

No change.

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16
Q

Explain why doubling the concentration doubles the rate of reaction.

A

Doubling the concentration doubles the number of particles in the same volume. This doubles the frequency of successful collisions.

17
Q

What effect does increasing the temperature have in terms of collision theory?

A

It gives particles more energy so they are more likely to collide with enough energy to react.

18
Q

How can you tell on a graph when equilibrium has been reached?

A

Both lines are horizontal.

19
Q

What is Le Chatelier’s principle?

A

When a change in conditions is imposed on a system at equilibrium, the system responds in a way that counteracts this change.

20
Q

How does a catalyst affect the rate of reaction?

A

It provides an alternative pathway which has a lower activation energy.

21
Q

How is equilibrium reached?

A

When in a closed system the forward and reverse reactions happen at the same rate.