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A Level Chemistry - physical chemistry > Redox Equlibria > Flashcards

Redox Equlibria Flashcards

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1
Q

What is oxidation and what is reduction

A

Oxidation is loss of electrons

Reduction is gain of electrons

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2
Q

What is an oxidising agent

A

A species that accept electrons while reducing another species

Electron pair acceptor

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3
Q

What is a reducing agent

A

A species that donates electrons to another species and they themselves are oxidised

Electron pair doner

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4
Q

What is meant by half cell

A

Is metal with metal ions in a solution

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5
Q

How does emf occur

A

As two different electrodes are connected,the potential difference between the two electrodes will cause a current to follow

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6
Q

What is the role of the salt bridge and what is it made from

A

It allows for ions to follow from one solution to the next to maintain the charge/complete the circuit

It’s a piece of filter paper that is saturated with a solution of KNO3 and NH4NO3

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7
Q

What is an electrochemical cell

A

The combination of two electrodes together

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8
Q

State what each electrode undergoes when current flows

A

The positive electrode is the one that favours the most reduction ie

The negative electrode will always favour oxidation

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9
Q

Why is the emf of the hydrogen electrode 0

A

By definition

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10
Q

In an electrochemical series what element will be the most powerful reducing agent

A

The one with the most negative value

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11
Q

In an electrochemical series which element will be the best oxidising agent

A

The one with the most positive value

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12
Q

What are the conditions for the standard hydrogen electrode and what is it used

A

Temperature at 298k
Pressure of 1atm
The species involved have a concentration of 1.0 mol dm-3
Platinum electrode

It’s used to measure the electrode potential of a half cell

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13
Q

State the direction of reaction fits its positive or negative

A

More negative it’s goes to the left

More positive goes to the right

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14
Q

How do you work out emf

A

EHRs-Elhs

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15
Q

State the difference between rechargeable and non rechargeable batteries

A

The current in rechargeable batteries can be reversed

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16
Q

What is meant by standard electrode potential

A

The emf of a half cell measured relative to the standard hydrogen electrode

17
Q

State the direction the negative and positive half cell go

A

Negative will go backwards (oxidise

Positive will go forwards reduce

18
Q

State the effect of concentration on E cell

A

If concentration of the reactants is increased e cell will increase

Same if concentration of products decreases

19
Q

State the effect of temperature on e cell (fowatd reaction is exothermic)

A

If the temp increase their will be a decrease in e cell

If temp decrease increase due to le Chatiler

20
Q

What is Ecell and what determines if the reaction happens

A

How far from equilibrium the cell reaction is how positive it is

21
Q

When are cells non rechargeable

A

When the reactions/currents are non-reversible

22
Q

Give the use of lithium ion cells

A

To power camera

Mobile phones

23
Q

Why isn’t water used as a solvent in the lithium ion cell

A

As it will react with the lithium metal

24
Q

What is the support medium in the lithium ion and what does it allow

A

It enables the ion to react with each other

Powdered graphite is the support medium

25
Q

Give the equations for the lithium ion cell

A

Li+ +CoO2+e- ->Li+[CoO2]-
Positive

Li+ +e-> Li negative electrode

Li +CoCO2->LiCoCO2

26
Q

What is a fuel cell give the overall reaction in a hydrogen fuel cell

A

It will use energy from the reaction of a fuel with oxygen in order to create a voltage they don’t need to be recharged

2H2+O2-> 2H20=1.23

27
Q

Why aren’t standard conditions used in a fuel cell

A

The rate is too slow to produce an appreciable current

28
Q

Give advantages of a hydrogen fuel cell

A

Less pollution and co2

Greater effecincy

29
Q

Give limitation of a hydrogen fuel cell

A

Expensive
Use of toxic chemicals
Limited life time
Storing of hydrogen

30
Q

State ways hydrogen can be stored in fuel cells

A

As a liquid under pressure

Adsorbed on the surface of a solid material or within a solid material

31
Q

State why fuel cells maintain a constant voltage

A

They are continuously fed with fresh o2 and H2

32
Q

What is the platinum electrode used for

A

To allow transfer of electrons

A Level Chemistry - physical chemistry (8 decks)

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