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AQA Science
Chemistry
P2.The Rate and Extent Of Chemical Change
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Created by
Alex Mendez
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Cards (30)
What can chemical reactions occur at?
Vastly different
rates
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What is a significant factor in how fast chemical reactions proceed?
Reactivity
of chemicals
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What can be manipulated to speed up or slow down chemical reactions?
Temperature
Concentration and Pressure
Surface Area
Presence of Catalyst
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Who determines the effect of different variables on reaction rate in industry?
Chemists
and
chemical engineers
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What do chemists and chemical engineers optimize in their processes?
Product yield
and
reaction time
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What is the formula for mean rate of reaction using reactants?
Mean rate = quantity of reactant used /
time taken
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What is the formula for mean rate of reaction using products?
Mean rate =
quantity of product formed
/ time taken
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How can the quantity of reactant or product be measured?
By
mass
in
grams
or
volume
in
cm³
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What are the units of rate of reaction?
g/s
or
cm³/s
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What additional units are required for Higher Tier students?
mol/s
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How can students calculate the mean rate of a reaction?
From
quantity of reactant
used and
time taken
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What should students be able to draw and interpret regarding reactions?
Graphs showing
quantity
of
product
against
time
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What can students use the slope of a tangent to measure?
The
rate of reaction
at a specific time
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What factors affect the rates of chemical reactions?
Concentration
,
pressure
,
surface area
,
temperature
,
catalysts
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How does increasing concentration affect reaction rates?
It increases the
frequency
of collisions
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What does collision theory explain?
For particles to react they must collide with sufficient energy.
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What is the minimum energy required for particles to react called?
Activation energy
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How does increasing temperature affect reaction rates?
It increases
collision frequency
and energy
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What do catalysts do in chemical reactions?
Change the
rate
without being used up
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How do catalysts increase reaction rates?
By providing a pathway with lower
activation energy
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What are reversible reactions?
Reactions where
products
can form
reactants
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How can the direction of reversible reactions be changed?
By changing the
conditions
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What happens if a reversible reaction is exothermic in one direction?
It is
endothermic
in the opposite direction
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What is reached when a reversible reaction occurs in a closed system?
Equilibrium
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What does Le Chatelier’s Principle predict?
The system responds to
counteract
changes
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What happens if the concentration of a reactant is increased?
More
products
will be formed
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What happens if the concentration of a product is decreased?
More
reactants
will react
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How does increasing temperature affect products at equilibrium in an endothermic reaction?
Relative
amount of products increases
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How does decreasing temperature affect products at equilibrium in an exothermic reaction?
Relative
amount
of
products increases
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What happens to equilibrium position with increased pressure in gaseous reactions?
Shifts towards the side with
fewer molecules
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