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Chemistry
Chemistry: Paper 1
C5
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Created by
Kathryn Roberts
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Cards (22)
What is conserved in chemical reactions?
Energy
is conserved in chemical reactions.
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What happens to the overall amount of energy in the universe after a chemical reaction?
The
overall
amount
of
energy
in
the
universe
remains
the
same.
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What type of reaction takes in energy from the surroundings?
An
endothermic
reaction takes in energy from the surroundings.
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How is an endothermic reaction indicated in terms of temperature?
It is shown by a
fall
in temperature.
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What are examples of endothermic reactions?
Thermal decompositions
Citric acid
+ sodium hydrogencarbonate
Used in some
sports injury packs
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What type of reaction transfers energy to the surroundings?
An
exothermic
reaction transfers energy to the surroundings.
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How is an exothermic reaction indicated in terms of temperature?
It is shown by a
rise
in temperature.
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What are examples of exothermic reactions?
Combustion
Neutralisation
Most
oxidation
reactions
Used in
self-heating
cans and hand warmers
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What is activation energy?
Activation energy is the minimum amount of energy that
reactants
need to react.
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What is the difference between bond breaking and bond forming in terms of energy?
Bond breaking is
endothermic
(energy absorbed).
Bond forming is
exothermic
(energy released).
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In endothermic reactions, what is true about the energy used to break bonds compared to the energy released by forming new bonds?
The energy used to
break
bonds is
greater
than the energy
released
by
forming
new
bonds.
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In exothermic reactions, what is true about the energy released by forming bonds compared to the energy used to break existing bonds?
The energy released by forming bonds is
greater
than the energy used to break existing bonds.
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What is a cell in the context of electrochemical cells?
A simple cell allows the charge to flow.
Reactions between electrolyte and
electrodes
set up a
charge difference
.
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What do electrochemical cells use to produce electricity?
They use
chemical reactions
to produce electricity.
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What is a battery?
A battery is two or more
cells
connected in series.
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What happens to non-rechargeable cells and batteries once one reactant is used up?
They
can't
be
recharged.
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What is the characteristic of rechargeable cells and batteries?
The
reaction
in the cell is
reversible
.
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What is the anode reaction in a hydrogen fuel cell?
The anode reaction is \(
H_2
\rightarrow 2H^+ + 2e^- \).
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What is the cathode reaction in a hydrogen fuel cell?
The cathode reaction is \(
O_2
+ 4H^+ + 4e^- \rightarrow 2H_2O \).
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What is the overall equation for the reaction in a hydrogen fuel cell?
The overall equation is \( 2H_2 +
O_2
\rightarrow 2H_2O \).
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What are the advantages of hydrogen fuel cells compared with batteries?
Less pollution over cell's
lifetime
.
Don't need
recharging
/
replacing
as often.
Cheaper
to make.
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What are the disadvantages of hydrogen fuel cells compared with batteries?
Storage of
H₂
gas takes up more space.
H₂ production can emit
greenhouse gases
.
H₂ is
explosive
- hard to store safely.
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