Chapter 23 - Redox And Electrode Potentials Flashcards

1
Q

Define redox

A

A reaction in which both reduction and oxidation take place.

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2
Q

Define oxidation

A

The loss of electrons or an increase in oxidation number.

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3
Q

Define reduction

A

The gain of electrons or a decrease in oxidation number.

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4
Q

what is an oxidising agent?

A

The oxidising agent:

1) takes electrons away from the atom that is oxidised
2) contains the atom that is reduced

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5
Q

what is a reducing agent?

A

a reducing agent:

1) adds electrons to the atom that is reduced
2) is itself oxidised

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6
Q

What is the Manganate half reaction?

A
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7
Q

how can redox reactions be written from oxidation numbers?

A

increase in oxidation number = decrease in oxidation number for another atom

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8
Q

What is the iodine + sodium thiosulphate reaction?

A
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9
Q

Why is there no clear colour change at the end point of a Vanadium and Potassium Manganate titration?

A

KMnO(4) is purple/pink

V2+ is violet

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10
Q

What property does the voltmeter have in a cell?

A

High resistance

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11
Q

Which way does the current flow in the cell?

A

Negative electrode to the positive electrode

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12
Q

How do the ions flow between cells?

A

ions flow across the Salt bridge

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13
Q

What is the salt bridge generally made of?

A
Potassium nitrate (KNO3)
Ammonium nitrate (NH4NO3)
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14
Q

What is the electrode made of in a standard hydrogen cell?

A

Platinum

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15
Q

What is in the half cell of Fe3+ and Fe2+?

A

Inert Pt electrode and Equimolar Fe2+ and Fe3+ (1 mol dm^-3)

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16
Q

When two half cells are connected, which is oxidised and which is reduced?

A

More reactive metal is oxidised

Less reactive metal is reduced

17
Q

Define standard electrode potential

A

The emf of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol/dm^3 and a gas pressure of 100kPa.

18
Q

What is the electrode potential of a hydrogen half cell?

A

0.00V

19
Q

What is the electrode potential of the cell?

A

Electrode potential of the positive terminal minus the electrode potential of the negative terminal

20
Q

How do we know if a cell is feasible?

A

If the electrode potential of the cell is positive, the reaction is feasible.

21
Q

what’s the Eo of a cell equation?

A

Eo cell = Eo (positive electrode) - Eo (negative electrode)

22
Q

what are metal/metal ion half cells?

A

the half cell is a metal rod dipped in a solution of its metal ion

23
Q

what is an ion/ion half cell?

A

An ion/ion half cell is a solution containing ions of the same element in different oxidation states

24
Q

what is electrode potential?

A

electrode potential, E, is the tendency for electrons to be gained and for reduction to take place in a half cell

25
Q

how do you measure a standard electrode potential?

A

To measure electrode potential, the half cell is connected to a standard hydrogen potential.

1) the electrodes are connected by a wire to allow a controlled flow of electrons through a voltmeter
2) The two solutions are connected by a salt bridge
3) The salt bridge contains ions

26
Q

what does the more negative the Eo value mean?

A

The more negative the Eo value

1) it’s more likely to lose electrons and undergo oxidation
2) the less the tendency to gain electrons and undergo reduction